Sourdough Sweet Potato Casserole Cookies

These Sourdough Sweet Potato Casserole Cookies transform the classic Thanksgiving side dish into an irresistible fall cookie! The light and fluffy brown butter cookies have a subtle sweet potato flavor and crunchy edges with the lightest touch of chew, while gooey marshmallows and crunchy brown sugar pecan streusel complete the sweet potato casserole experience. Every bite is soft, chewy, crisp, and perfectly nostalgic!

Perfect For…

• Thanksgiving dessert tables: Serve these alongside the pies for a fun, handheld twist on classic sweet potato casserole.
• Friendsgiving gatherings: They are easy to transport, share, and enjoy without plates or utensils.
• Fall parties and potlucks: The warm spices, marshmallows, and pecan streusel make them especially fitting for autumn celebrations.
• Holiday hostess gifts: Package the cookies in a bakery box for a thoughtful homemade treat inspired by a nostalgic holiday favorite.

Essentials for the Perfect Sourdough Cookie

• Digital Kitchen Scale: In my kitchen, a digital scale is a non-negotiable! I have had this exact digital scale for years, and it has never failed me. Measuring by weight is the only foolproof way to ensure accuracy, especially when reducing the sweet potato puree and measuring flour and sourdough starter.
• Stand Mixer: A quality stand mixer makes it easy to combine this thick dough without over-mixing, which is key for maintaining a soft and tender center.
• Large Cookie Scoop: A large cookie scoop creates uniform 3-tablespoon cookies so they bake evenly every time!

Ingredients

For The Sourdough Sweet Potato Cookies

• ½ cup salted butter (113g): Browning the butter adds a deep, nutty caramel flavor that pairs perfectly with sweet potato and brown sugar. To use unsalted butter, add ¼ tsp additional salt.
• ⅔ cup plain canned sweet potato puree (166g): Use plain sweet potato puree without added sugar or spices. Cooking it down concentrates the naturally light sweet potato flavor while removing excess moisture. You should have approximately 70g after reducing.
• ¾ cup light brown sugar, packed (165g): Brown sugar provides the deep, caramel-like sweetness associated with sweet potato casserole while helping the cookies remain soft.
• ¼ cup granulated sugar (50g): Granulated sugar balances the moisture from the puree and helps the cookies spread without becoming overly thin.
• ⅓ cup sourdough starter, active or discard, stirred down (125g): Active or discard starter works! Stir it down well before measuring by volume. For best accuracy, measure by weight.
• 1 large egg yolk (20g): Using only the yolk provides richness and structure without adding the excess moisture found in a whole egg.
• 1 tsp vanilla extract (5g): Pure vanilla extract rounds out the warm brown sugar and sweet potato flavors.
• ¾ tsp ground cinnamon: Cinnamon adds just enough warmth to create that classic sweet potato casserole flavor without overpowering the sweet potato.
• ¾ tsp salt (4.5g): Sea salt is preferred over iodized salt for a cleaner flavor profile.
• 1½ cups all-purpose flour, scooped (not spooned or sifted) (237g): I designed this measurement to be scooped directly out of the bag rather than spooned and leveled. Pro Tip: For the best accuracy and overall cookie texture, measure flour by weight.
• 1 tsp baking soda (6g): Ensure you are using baking soda, not baking powder. They are not interchangeable here.
• Approximately 1¼ cups mini marshmallows: You will need about 8 mini marshmallows for the center of each cookie. They melt together in the oven to create that signature gooey sweet potato casserole topping!

For The Pecan Streusel “Casserole Topping”

• 3 tbsp salted butter, melted (42g): Melted butter binds the streusel together and helps it bake into crisp, buttery clusters.
• ⅓ cup all-purpose flour (53g): Flour gives the streusel structure and creates the crunchy contrast that makes these cookies so special.
• ⅓ cup light brown sugar, packed (73g): Brown sugar creates a caramelized, casserole-inspired crunch.
• ¼ tsp ground nutmeg: Using nutmeg in the streusel adds another layer of warm flavor without overwhelming the sweet potato cookie with too many spices.
• ½ cup finely chopped pecans (optional): Pecans complete the classic sweet potato casserole flavor and add even more crunch. They may be omitted or substituted for chopped walnuts if needed.

How to Make Sourdough Sweet Potato Casserole Cookies

Step 1: Brown the Butter & Chill

Place butter in a small saucepan over medium-low heat. Cook for about 5–7 minutes, stirring constantly. It will foam up, then the foam will dissipate and it will quickly turn golden, develop brown flecks, and take on a nutty caramel aroma.

Remove the browned butter from heat, transfer to a shallow bowl, and place in the fridge until it firms back into a “dent soft” consistency (about 1 hour in the fridge). “Dent soft” means it is opaque and solid but still pliable. When pressed with a finger, it should indent with some resistance and feel cool to the touch, not oily or greasy.

Step 2: Reduce & Chill the Sweet Potato

Place the canned sweet potato puree in a small saucepan over medium-low heat. Cook, stirring frequently, until the puree thickens into a concentrated paste and most of the excess moisture evaporates, about 10 minutes. It should be very thick and have deepened in color. You should have approximately 70g remaining. Transfer it to a small refrigerator-safe dish and chill completely. Note: This is a critical step, and you cannot skip it for these cookies.

Sweet potato puree contains both moisture and starch. Reducing it concentrates the flavor, but using too much can leave the centers of the cookies gummy and unstable. Cooking it down helps to create the proper flavor and structure.

Step 3: Prepare the Pecan Streusel

Preheat oven to 350°F (175°C). Line a small baking sheet with parchment paper.

Combine the melted butter, flour, brown sugar, nutmeg, and chopped pecans. Fluff and stir the mixture with a fork until uneven crumbs and clusters form.

Spread the streusel over the prepared baking sheet. Bake for approximately 13–14 minutes, or until golden around the edges. Allow it to cool completely before breaking it into small crunchy clusters.

The streusel will continue to crisp as it cools. Baking it separately is what preserves its crunch and creates the best contrast against the soft cookie and gooey marshmallows.

Step 4: Preheat & Prep

Keep oven preheated to 350°F (175°C). Line two baking sheets with parchment paper.

Before baking the cookies, divide the mini marshmallows into small groups of 8 marshmallows each. Having them ready will allow you to top the cookies quickly in a future step.

Step 5: Cream the Butter & Sugars

Beat the brown sugar, granulated sugar, and cooled brown butter until the texture is creamy, uniform, and slightly aerated. If you see chunks of butter remaining, keep mixing! This works best with a stand mixer fitted with a paddle attachment or a handheld electric mixer.

Step 6: Add the Wet Ingredients

Add the cooled reduced sweet potato, sourdough starter, egg yolk, vanilla extract, cinnamon, and salt. Beat until smooth and slightly frothy.

Pro Tip: Scrape down the sides and bottom of the bowl to ensure the sweet potato and sourdough starter are completely incorporated with no streaks remaining.

Step 7: Incorporate the Dry Ingredients

Add the flour and sprinkle the baking soda evenly over the top. Turn the mixer to low speed and stir until just combined. The dough will be thick.

Critical Step: Stop mixing as soon as the flour is incorporated. Over-mixing can develop too much gluten and make the cookies tough instead of soft with a subtle chew.

Step 8: Scoop

Portion the dough into large scoops using a cookie scoop or spoon (3 tbsp / about 60g each). Place up to 8 scoops per baking sheet (in a 3-2-3 pattern) to allow enough space for spreading.

Step 9: Bake & Add Marshmallows

Bake for 12 minutes. Remove the pan from the oven, close the oven door, and quickly press 8 mini marshmallows into the center of each cookie. Rotate the pan, return it to the oven, and bake for 5–7 minutes longer.

The edges of the cookies should look set, while the marshmallows should be puffed, melty, and beginning to join together. Bake in batches. Recipe makes 13 large cookies.

Step 10: Add the Streusel

Immediately after removing the cookies from the oven, press pieces of the baked pecan streusel into and around the melted marshmallow topping. Press gently so the streusel adheres to the gooey marshmallows without flattening the cookies.

Step 11: Cool On Baking Sheet

Allow cookies to set on the hot baking sheet for 10 minutes before transferring them to a wire rack.

Let the cookies finish cooling on the wire rack before serving. The centers will be very delicate while warm but will develop their final light, fluffy, and subtly chewy texture as they cool.

Storage Tips

Store completely cooled cookies in an airtight container at room temperature for up to 5 days. For best results, arrange them in a single layer to protect the marshmallow and streusel topping.

Why This Recipe Works

Every component of this recipe is designed to recreate the flavor and texture of sweet potato casserole, but in a cookie form that’s easy to hold, not too sweet, and not too savory. Reducing the puree lightly concentrates the naturally subtle sweet potato flavor while controlling its moisture and starch. Brown butter, brown sugar, and cinnamon complement that flavor without overpowering it, creating a cookie that is soft and fluffy with the slightest touch of chew, just like a marshmallow-topped sweet potato casserole.

The toppings complete the casserole experience. Melted marshmallows add a distinctly gooey and chewy layer, while the separately baked pecan streusel stays crisp and crunchy. Together, the fluffy cookie, chewy marshmallows, and crisp streusel create the same satisfying contrast found in a classic sweet potato casserole!

The Sourdough Cookie Lady’s Tips

• Weigh the reduced sweet potato. Begin with the full ⅔ cup (166g) of puree, then cook it down until approximately 70g remains. Too much moisture in the sweet potato puree can leave the centers gummy and unstable. I haven’t tested this recipe with homemade sweet potato puree, but if you test it this way please share your experience in the comments!
• Chill both components completely. The reduced sweet potato should be cold, and the browned butter should return to an opaque, “dent soft” consistency before mixing the dough. Warm ingredients can cause excess spreading.
• Bake the streusel separately. This is the secret to keeping it crisp! I tested baking this directly on top of the cookie, but it absorbed too much moisture and lost its crunchiness!
• Prepare the marshmallows before baking. Arrange them into groups of 8 so you can top the partially baked cookies quickly. Pause the timer while the pan is out of the oven and count only actual oven time for the bake times listed.
• Cool the cookies before transferring. Cool the cookies on the hot baking sheet for 10 minutes, then transfer them to a wire rack and allow them to finish cooling. The delicate centers need this time to develop their final structure.

Frequently Asked Questions

What do sweet potato casserole cookies taste like?

These sourdough sweet potato casserole cookies have a light sweet potato flavor complemented by brown butter, brown sugar, cinnamon, and nutmeg. During testing, I discovered that the more sweet potato you add to the dough, the gummier and flatter it becomes. I finally landed on this balance of perfect texture, but the sweet potato flavor is light and slightly understated. This recipe relies on the fluffy texture, gooey marshmallows, and crunchy pecan streusel to bring everything together so the complete cookie tastes like sweet potato casserole.

Why do I have to reduce the sweet potato puree?

Canned sweet potato puree adds both moisture and starch to the dough. Using too much can cause the cookies to spread unpredictably or leave the centers gummy and unstable. Reducing ⅔ cup (166g) of puree down to approximately 70g concentrates the sweet potato flavor while controlling the moisture. Do not skip this step or add the full amount of unreduced puree directly to the dough.

Are these sweet potato cookies cakey?

These cookies are intentionally lighter and fluffier than my usual dense and chewy sourdough cookies, but they still have a subtle chew and a substantial cookie texture. The softer center resembles the sweet potato filling in a real casserole, while the marshmallows add a more pronounced chewy texture and the streusel provides crunch.

Do I have to chill the dough?

No! Once the brown butter and reduced sweet potato puree have been chilled as directed, the finished cookie dough can be scooped and baked immediately. There is no additional dough-chilling time required unless you choose the long-fermentation option.

Will these cookies taste sour?

No! The sourdough starter acts as a flavor enhancer, adding subtle depth that balances the sweet marshmallow and streusel topping. To prevent a noticeably sour flavor, use active starter or discard that has been fed within the last two weeks. A long fermentation will create a more developed sourdough flavor.

Can I Freeze Sourdough Cookie Dough?

Absolutely! For best results, freeze the plain sweet potato cookie dough without the marshmallows or streusel:

1. Scoop: Portion the cookie dough into scoops (3 tbsp / about 60g each) and place them on a parchment-lined baking sheet. They can be close together, but make sure they are not touching.
2. Flash Freeze: Place the sheet in the freezer for approximately 1 hour, or until the dough scoops are firm to the touch.
3. Store: Transfer the frozen dough scoops to a gallon freezer bag. Store in the freezer for up to 3 months. Wait to add the marshmallows and streusel until you bake the cookies.

Pro Tip: Double the recipe and intentionally freeze an extra batch! This gives you ready-to-bake sweet potato sourdough cookies whenever that sweet tooth hits. Then all you have to do is prep the streusel and top with marshmallows!

Tips For Baking Frozen Dough:

Thaw Partially: For the closest result to freshly prepared dough, allow frozen dough scoops to sit at room temperature for 30–60 minutes before baking.

Add the Toppings During Baking: Follow the regular two-part baking method. Bake the cookies for 12 minutes, add the marshmallows, then return them to the oven for the remaining 5–7 minutes. Press the baked streusel into the melted marshmallows immediately after baking.

Potentially Increase Bake Time: If the dough is still colder than freshly prepared dough, it may need an additional 1–2 minutes of oven time.

How to Make Long-Fermented Sourdough Sweet Potato Casserole Cookies

To long-ferment the dough for more developed sourdough flavor, follow these simple directions:

1. Prepare & Scoop: Follow the recipe directions to prepare the cookie dough. Portion the dough into scoops (3 tbsp / about 60g each) and arrange them in a tightly covered container or on a tightly covered baking sheet. Keep the mini marshmallows and streusel separate.
2. Cold Ferment: Refrigerate the covered dough scoops for up to 48 hours.
3. Bring to Room Temp: Remove the dough scoops from the refrigerator and allow them to sit at room temperature for approximately 30 minutes before baking. This helps the cookies spread similarly to a same-day batch.
4. Bake: Follow the regular baking directions. Bake for 12 minutes, add the mini marshmallows, and bake for an additional 5–7 minutes. Press the baked streusel into the melted marshmallows immediately after baking.

Note: Dough may be refrigerated for a maximum of 72 hours, but it can begin losing some of its structure beyond the 48-hour mark.

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