If you’re looking for a fall dessert that’s soft, moist, and packed with just the right amount of pumpkin flavor, these potato flake sourdough pumpkin bars are it. They’re made with a fermented batter using a potato flake sourdough starter.
These bars land somewhere between pumpkin cake and pumpkin brownie — soft like cake, but a little more dense and fudgy. They might just end up at the top of my favorites list.
This recipe is a great way to use your existing starter (active or discard) and add a little extra depth to your baking. The fermentation gives them a tenderness that is just amazing!
Top them with a silky Coffee Maple Glaze and you’ll notice those bad boys disappearing fast at gatherings. It’s also the perfect companion to your morning coffee and a wonderful way to show off the hard work that goes into feeding your starter and creating something delicious from it.
What Makes These Pumpkin Bars Different
If this is your first time baking a sweet treat with your own starter, this is a great place to begin. The long fermentation process is the secret behind their soft texture and deep flavor. Letting the batter ferment in a warm place overnight allows the wild yeast to gently rise and work its magic.
The result? A batch of pumpkin bars that are:
- Moist and tender, thanks to the 1/4 cup of starter in the batter
- Perfectly balanced between cake and brownie texture
- A delicious way to add to favorite sourdough discard recipes
- Naturally flavored with warm spices
It’s the best way to enjoy pumpkin season!
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Tools You’ll Need
- Large bowl or stand mixer
- Wooden spoon or hand mixer
- Rubber spatula
- 8×8 baking dish
- Cooling rack
- Measuring cups and spoons
Optional:
- Offset spatula for spreading glaze evenly across the top of the bars
Ingredients
For the fermented batter
- 1 cup all-purpose flour
- 1 egg
- ¼ cup potato flake starter (active or discard)
- 1 cup pumpkin purée (homemade pumpkin puree or canned)
- ⅔ cup brown sugar
- ½ cup melted coconut oil
- 1 teaspoon vanilla extract
After fermentation
- ½ teaspoon baking soda
- ½ teaspoon salt
- 1 teaspoon cinnamon
- ½ teaspoon pumpkin pie spice
Coffee Maple Glaze
- 1 tablespoon unsalted butter, melted
- 1–2 cups powdered sugar (adjust for your preferred thickness)
- 2 tablespoons espresso or strong brewed coffee (if you don’t love coffee, replace with milk)
- ⅛ teaspoon maple extract
- ¼ teaspoon pumpkin pie spice
Instructions
Mix the fermented batter
In a large mixing bowl whisk together the dry ingredients — flour and brown sugar — until no clumps remain. This helps evenly distribute the sugar before you add the wet ingredients.
Add the wet ingredients: egg, melted coconut oil (cool, not hot), vanilla extract, pumpkin purée, and starter. Using a hand mixer, mix until smooth and well combined. Scrape down the sides of the bowl as needed to make sure all the dry spots are incorporated.
The batter should be thick and silky — not runny, but not stiff either. If it looks too dry, add a small splash of milk or water to loosen it up. This ensures the fermentation happens evenly during the resting period.
Ferment the batter
Cover the bowl with plastic wrap or a loose-fitting lid and let it rest in a warm place for 8–12 hours, or overnight. A turned-off oven with the light on or a warm corner of your kitchen works great.
During this first rise, the natural yeast and bacteria in your potato flake sourdough starter act as a leavening agent, breaking down the flour and developing a depth of flavor unique to potato flake sourdough recipes.
By the end of the fermentation, the batter may look slightly puffed or have small bubbles on the surface — that’s exactly what you want!
Preheat and prepare
When you’re ready to bake, preheat your oven to 350°F (175°C). Grease an 8×8-inch baking dish well with butter, coconut oil, or nonstick spray. You can also line it with parchment paper for easy removal later.
Add the final ingredients
To your fermented batter, add the baking soda, salt, cinnamon, and pumpkin pie spice. These additions act as your final lift and flavor balance. Stir gently with a spatula or spoon just until everything is evenly mixed — overmixing at this point can cause your bars to have a chewy texture.
If you’d like to add chocolate chips, chopped pecans, or even a swirl of maple syrup, this is the time to fold them in.
Bake
Pour the finished batter into your greased baking dish, smoothing out the top with a spatula so it bakes evenly.
This is also a good time to gather your Coffee Maple Glaze ingredients so you are ready when the bars come out of the oven.
Bake for 20–25 minutes, or until the top of the bars springs back when lightly pressed in the center. You can also check doneness by inserting a toothpick — it should come out mostly clean, with just a few moist crumbs attached.
Place the dish on a wire rack and let the bars cool in the pan.
Cool and glaze
Once completely cooled, whisk together your Coffee Maple Glaze ingredients in a small bowl. Start with 1 cup of powdered sugar and add more as needed to reach your desired thickness.
Drizzle the glaze over the cooled pumpkin bars and spread it evenly with a spatula or the back of a spoon. Allow the glaze to set for at least 15–20 minutes before slicing.
If you want an extra treat, sprinkle a few chocolate chips or a drizzle of maple syrup across the top before serving.
Ingredient Substitutions
- Flour: You can substitute freshly milled soft white wheat flour. You might need to add 1/4 cup more starter if it is too thick. (FMF can soak up more than regular flour)
- Coconut oil: Melted butter works great if you prefer a richer flavor.
- Brown sugar: Swap for 2/3 cup sugar or use maple syrup for a lighter sweetness.
- Pumpkin purée: Homemade pumpkin puree is always a bonus if you have extra from another recipe.
- Coffee in the glaze: Replace with milk if you’d rather skip the coffee flavor.
- Add-ins: Fold in chocolate chips or chopped pecans before baking for extra texture.
- Maple Extract: If you don’t have maple extract on hand (I highly recommend you get some.) You can use a bit of maple syrup in place of the extract and slightly reduce the coffee in the glaze to compensate for the extra liquid. You can also use vanilla extract in place of maple if you prefer.
Frequently Asked Questions
Can I skip the fermentation step?You can, but the long fermentation process adds so much flavor and tenderness. Even a shorter ferment (about 4 hours in a warm place) makes a big difference.
Can I double the recipe?Yes! Use a 9×13 baking dish and add about 5–10 minutes to your bake time.
Can I freeze these pumpkin bars?Absolutely. Once cooled and glazed, store in a freezer-safe bag with parchment between layers. Thaw at room temperature for the best results.
How do I know when they’re done?The top should bounce back when lightly pressed in the center — that’s the best way to tell.
How should I store leftovers?Cover tightly and store at room temperature up to 2 days, or refrigerate for up to 5. They’re just as good the next time you enjoy them.
What’s the texture like?Soft, moist, and slightly fudgy — these bars are somewhere between pumpkin bread and cake.
Tips for the Best Results
- Make sure your cup of the starter is at room temperature before mixing this prevents the coconut oil from solidifying.)
- Don’t overbake — check the top of the bars for that soft bounce.
- If your home is cool, place the batter in a warm place during fermentation.
- Feed starter regularly — a healthy starter gives the best flavor and rise.
Serving Ideas
These bars are wonderful on their own, but here are a few ideas to make them extra special:
- Add a drizzle of maple syrup or sprinkle of cinnamon sugar before serving.
- Pair with your morning coffee or a mug of hot chocolate.
Why You’ll Love This Recipe
If you love fall flavors from the recipes like pumpkin cinnamon rolls or potato flake sourdough pumpkin bread, this is you next must try!
I really love that this recipe is a wonderful way to use that discard you have sitting in the fridge to make something sweet, cozy, and simple. The batter comes together easily — no fancy tools or techniques needed — and it’s a delicious way to use that cup of starter you’ve been maintaining.
When life gets busy, it’s nice to have a recipe that brings results without a lot of fuss. These bars are quick to prepare, forgiving, and they showcase all the best parts of potato flake sourdough baking — a little patience, a touch of science, and a whole lot of flavor.
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Potato Flake Sourdough Pumpkin Bars with Coffee Maple Glaze
Equipment
- Large bowl or stand mixer
- Wooden spoon or hand mixer
- Rubber Spatula
- 8×8 baking dish
- Cooling Rack
- measuring cups and spoons
- Optional: Offset spatula for spreading glaze evenly
Ingredients
Fermented Batter
- 1 cup all-purpose flour
- ⅔ cup brown sugar
- 1 egg
- ¼ cup potato flake starter active or discard
- 1 cup pumpkin purée
- ½ cup melted coconut oil
- 1 teaspoon vanilla extract
After Fermentation
- ½ teaspoon baking soda
- ½ teaspoon salt
- 1 teaspoon cinnamon
- ½ teaspoon pumpkin pie spice
Coffee Maple Glaze
- 1 tablespoon unsalted butter melted
- 1 –2 cups powdered sugar adjust for desired thickness
- 2 tablespoons espresso or strong brewed coffee or milk if preferred
- ⅛ teaspoon maple extract
- ¼ teaspoon pumpkin pie spice
Instructions
- In a large bowl, whisk together the flour and brown sugar to break up any clumps. Add the egg, melted (but not hot) coconut oil, vanilla, pumpkin purée, and potato flake starter. Mix with a hand mixer or wooden spoon until the batter is smooth and thick. Scrape down the sides of the bowl as needed.
- If the mixture seems too thick, add a small splash of milk or water to loosen it slightly.
- Cover the bowl with plastic wrap or a loose-fitting lid and let it rest in a warm spot for 8–12 hours, or overnight. The batter should puff slightly and may have small bubbles on top—signs that the fermentation worked.
- When ready to bake, preheat your oven to 350°F (175°C). Grease an 8×8-inch baking dish with butter, coconut oil, or nonstick spray, or line it with parchment paper for easy removal.
- Stir the baking soda, salt, cinnamon, and pumpkin pie spice into the fermented batter. Mix gently until just combined—overmixing can make the bars dense.
- Pour the batter into the prepared dish, smoothing the top evenly. Bake for 20–25 minutes, or until the center springs back lightly when pressed. A toothpick should come out mostly clean with a few moist crumbs.
- Set the dish on a wire rack and let the bars cool completely before glazing.
- In a small bowl, whisk together the melted butter, powdered sugar, espresso (or milk), maple extract, and pumpkin pie spice until smooth. Adjust thickness by adding more sugar or a splash more liquid as needed.
- Spread or drizzle the glaze evenly over the cooled bars. Let it set for 15–20 minutes before slicing. For an extra touch, sprinkle a few chocolate chips or drizzle with maple syrup before serving.
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