Frosted Sourdough Sugar Cookie Bars
Soft, buttery, and topped with a thick layer of buttercream, frosted sourdough sugar cookie bars are a fun and easy way to use up extra sourdough discard. They have that perfect chewy sugar cookie flavor and texture but in bar form. No rolling or cutting needed!
The sourdough discard adds a subtle tang that balances the sweetness, while the bars stay soft and chewy with a tender crumb. They’re perfect for holidays, celebrations, or just because you need a delicious, easy dessert.
Why you’ll love these cookie bars
✔ Uses sourdough discard – A great way to reduce waste.
✔ Easier than cut-out cookies – No chilling, rolling, or shaping needed.
✔ Super soft and chewy – The discard and butter keep them tender.
✔ Perfect for any occasion – Change up the frosting and decorations to fit any holiday!
I’ve got another cookie bar recipe on the blog too that uses chocolate chips and sourdough starter! Check out this sourdough cookie bars recipe.
Ingredients you’ll need
I’ve just added a quick run-down of what’s needed and why. You can find the exact amounts in the printable recipe card at the bottom of this post.
For the cookie bars
- Butter: For richness and flavor. This can be salted or unsalted.
- Granulated sugar: Sweetens and helps create a soft texture.
- Sourdough discard starter: Adds depth of flavor and slight chewiness.
- Egg yolk: Helps bind the bars and keeps them tender. I took away the egg white to reduce the water in the dough since we are bringing water in with the sourdough starter.
- Vanilla paste or extract: Essential for classic sugar cookie flavor. You could also bring in a hint of almond extract for extra flavor.
- All-purpose flour: Gives the bars structure.
- Baking powder & salt
For the frosting
- Butter: The creamy base of the frosting.
- Powdered sugar: Adds sweetness and structure.
- Vanilla extract: Enhances flavor.
- Milk or cream: To loosen the buttercream.
- Sprinkles and food color (optional)
Method
Here are some photos of how to make these frosted sourdough sugar cookie bars.
1. Cream butter and sugar
In a large bowl cream butter and sugar until light and fluffy. Take your time with this until it has lightened in color with a lovely creamy texture.
2. Add in egg and sourdough starter
Mix in the egg yolk, vanill and sourdough starter until creamy and combined.
3. Add dry ingredients
Lastly mix in the salt, baking powder and flour. Don’t over-mix it or it can make the cookies tough.
4. Add to pan
Press the mixture into a lined pan. The dough can be a bit sticky, so I place little pieces of dough all over the pan and then use my fingers to press it together. Then chill for 2 hours or up to 36 hours.
5. Bake and frost
Bake the sugar cookie bars until golden, then let them cool and frost.
Frosting
To make the frosting, beat butter, powdered sugar, vanilla, and a splash of milk or cream until smooth and fluffy. The longer you mix it the lighter and fluffier the buttercream will come. Add in food color if you want and top with sprinkles.
Tips
✔ Use room-temperature butter – It creams better with sugar.
✔ Don’t overmix the dough – Mix just until combined for the best texture.
✔ Cool completely before frosting – Otherwise, the frosting will melt.
✔ For extra flavor, add 1/2 teaspoon almond extract to the dough.
Storing & Freezing
- Store at room temp in an airtight container for up to 3 days or refrigerate for up to a week.
- Freeze frosted or unfrosted bars for up to 2 months.
More sourdough discard recipes
Frosted Sourdough Sugar Cookie Bars
Ingredients
- 113 g butter softened to room temperature
- 150 g granulated sugar
- 1 large egg yolk
- 50 g sourdough discard starter
- 1/12 teaspoons vanilla paste or extract
- 156 g all-purpose flour
- 3/4 teaspoon baking powder
- 1/4 teaspoon salt
Buttercream
- 85 g butter softened to room temperature
- 180 g powdered sugar
- 1-2 tablespoon heavy cream room temperature
- 1/8 teaspoon salt omit if using salted butter
- Pink food color and sprinkles optional
Instructions
- Line an 8×8-inch (20x20cm) baking pan with parchment paper, leaving an overhang so you can easily lift out the baked bar.
- In a large bowl, beat butter and sugar until fluffy, about 2-3 minutes with an electric mixer. Mix in sourdough discard, eggs, and vanilla until smooth.
- In a small seperate bowl, whisk together flour, baking powder, and salt. Add this to the butter mixture and mix until just combined.
- Spread dough evenly into the prepared pan. The dough can be a bit sticky, so I place little pieces of dough all over the pan and then use my fingers to press it together. Then chill for 2 hours or up to 36 hours.
- When ready to bake, heat the oven to 180°C (350°F).
- Bake for 25-28 minutes until lightly golden brown and the top is set. Let cool completely.
Buttercream
- In a bowl add the butter and powdered sugar. Starting on low, with an electric beat the butter and powdered sugar until combined. Add vanilla, and cream and beat on high speed until smooth and creamy and light. Add in food color if you like.
- Spread frosting over cooled bars and add sprinkles.
- Cut into 16 bars. For extra smooth cuts, chill the cookie slab in the fridge for an hour first to firm up the frosting.
Notes
Storing & Freezing
- Store at room temp in an airtight container for up to 3 days or refrigerate for up to a week.
- Freeze frosted or unfrosted bars for up to 2 months.
