These frosted sourdough sugar cookie bars are a fun, easy treat made with simple pantry staples and a touch of sourdough tang. They’re soft, buttery, and topped with a thick layer of creamy frosting—perfect for decorating with sprinkles, colored frosting, or leaving plain for a more classic vibe. Whether you’re baking for a celebration or just want something sweet and nostalgic, these bars are endlessly customizable and always a hit.
What makes these sourdough sugar cookie bars stand out?
- Depth of flavor: The sourdough starter adds a subtle tang that makes the flavor more complex and irresistible.
- Texture: They’re soft, thick, and perfectly chewy—like the best parts of a sugar cookie in bar form.
- Crowd pleaser: A fun, easy way to use up sourdough discard in a crowd-pleasing dessert.
- Convenience: Stay moist and tender for days, making them great for make-ahead treats.
Tips for Success
- Cool Completely: Allow the cookie bars to cool completely in the pan before cutting to prevent them from falling apart.
- Room Temperature Ingredients: Use room temperature ingredients to ensure even mixing and a smooth batter.
- Measure Accurately: Weigh your ingredients for precise measurements, especially the flour and sugar, to achieve the desired consistency.
- Sourdough discard: I recommend using discard no more than a week old as this may result in a sour result.
- Do Not Overmix: Mix the batter just until combined to avoid developing too much gluten, which can result in tough cookie bars.
How to make sourdough cookie bars: step-by-step
INGREDIENTS
- 113 grams unsalted butter (softened)
- 150 grams of sugar
- 1 large egg
- 100 grams of sourdough starter (fed or unfed & brought to room temp)
- 7 grams vanilla extract
- 140 grams of all-purpose flour
- 3 grams of baking powder
- 2 grams of salt
- 1 teaspoon cornstarch
- 80 grams of rainbow sprinkles
For the frosting:
- 2 tablespoons of unsalted butter (softened)
- 1 1/2 cups powdered sugar
- 2-3 tablespoons of heavy cream
- 1 teaspoon vanilla extract
- 1 drop of red food dye (for pink color-optional)
- a pinch of salt to cut the sweetness (optional)
Equipment
- 1 metal 9×9-inch baking pan (8×8 inch works too)
- parchment paper
- food scale
- mixing bowl
- hand mixer or stand mixer
Instructions
- Preheat the oven to 350°F (175°C). Line a 9×9 inch (or 8×8-inch) baking pan with parchment paper.
- Cream the butter and sugar together in a large bowl until light and fluffy (about 2–3 minutes). You can use a hand mixer or stand mixer for this step.
- Add the egg, sourdough starter, and vanilla extract to the bowl. Mix until well combined and smooth.
- In a separate bowl, whisk together the flour, baking powder, salt, and cornstarch.
- Gradually mix the dry ingredients into the wet mixture, stirring just until combined. Be careful not to overmix.
- Fold in the sprinkles using a spatula, making sure they’re evenly distributed throughout the dough.
- Spread the dough evenly into the prepared baking pan. Use a spatula or your hands to press it into the corners and smooth the top. Note: this is a wetter sugar cookie bar dough, this is normal. It helps achieve optimal texture.
- Bake for 28-35 minutes, or until the edges are lightly golden and a toothpick inserted into the center comes out clean. Note: if using an 8×8 inch pan you may need to bake the sugar cookie bars a little longer.
- Let the bars cool completely in the pan before frosting.
How to make the frosting
- In a medium bowl, beat the softened butter until smooth.
- Add the powdered sugar, 2 tablespoons of heavy cream, vanilla extract, 1 drop of red food dye, and a pinch of salt (if using). Beat until smooth and fluffy. Add the remaining tablespoon of cream if needed to reach your desired consistency.
- Spread the frosting over the cooled bars, then top with extra sprinkles if you’d like.
- Slice into squares and enjoy!
- Store the frosted bars in an airtight container at room temperature for up to 2 days, or refrigerate for up to 5 days for maximum freshness.
More sourdough dessert recipes
- Sourdough Blondies
- Sourdough Brownies
- Sourdough Discard Cinnamon Roll Muffins
- Sourdough Blueberry Bread
Sourdough Sugar Cookie Bars
These soft and chewy sourdough sugar cookie bars are topped with a rich, creamy frosting and have the perfect balance of tang and sweetness in every bite.
Servings:
16
bars
Equipment
- 1 metal 9x9-inch baking pan
- Parchment paper
- Food scale
- Mixing bowl
- Hand mixer/stand mixer
Ingredients
- 113 grams unsalted butter (softened)
- 150 grams sugar
- 1 large egg (room temperature)
- 100 grams sourdough starter (fed or unfed & brought to room temp)
- 7 grams vanilla extract
- 140 grams all-purpose flour
- 3 grams baking powder
- 2 grams salt
- 3 grams cornstarch
- 80 grams rainbow sprinkles
For the frosting
- 2 tablespoons unsalted butter (softened )
- 1 & 1/2 cups powdered sugar
- 2-3 tablespoons heavy cream
- 1 teaspoon vanilla extract
- 1 drop red food dye for pink frosting (optional )
- a pinch of salt to cut the sweetness (optional )
Instructions
-
Preheat the oven to 350°F (175°C). Line a 9x9 inch (or 8x8-inch) baking pan with parchment paper.
-
Cream the butter and sugar together in a large bowl until light and fluffy (about 2–3 minutes). You can use a hand mixer or stand mixer for this step.
-
Add the egg, sourdough starter, and vanilla extract to the bowl. Mix until well combined and smooth.
-
In a separate bowl, whisk together the flour, baking powder, salt, and cornstarch.
-
Gradually mix the dry ingredients into the wet mixture, stirring just until combined. Be careful not to overmix.
-
Fold in the sprinkles using a spatula, making sure they’re evenly distributed throughout the dough.
-
Spread the dough evenly into the prepared baking pan. Use a spatula or your hands to press it into the corners and smooth the top.Note: this is a wetter sugar cookie bar dough, this is normal. It helps achieve optimal texture.
-
Bake for 28–35 minutes, or until the edges are lightly golden and a toothpick inserted into the center comes out clean. Note: if using an 8x8 inch pan they may need a little longer to bake.
-
Let the bars cool completely in the pan before frosting.
How to make the frosting
-
In a medium bowl, beat the softened butter until smooth.
-
Add the powdered sugar, 2 tablespoons of heavy cream, vanilla extract, 1 drop of red food dye, and a pinch of salt (if using). Beat until smooth and fluffy. Add the remaining tablespoon of cream if needed to reach your desired consistency.
-
Spread the frosting over the cooled bars, then top with extra sprinkles if you’d like.
-
Slice into squares and enjoy!
-
Store the frosted bars in an airtight container at room temperature for up to 2 days, or refrigerate for up to 5 days for maximum freshness.
Notes
Sourdough discard: Ensure your sourdough discard is no more than week old to avoid a sour taste in the sugar cookie bars. Active starter can be used.
Baking pan: If using an 8x8 inch baking pan the cookie bars may need to bake slightly longer.
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