I can never resist these sourdough sugar cookie bars, with their soft buttery bite, chewy center, and thick swoop of buttercream on top. They look like Valentine’s Day bakery treats, but they’re made with sourdough discard.

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I’m obsessed with these Vanilla Sourdough Sugar Cookie Bars because they hit that chewy sugar cookie craving without the fussy little cookie routine. I love the way sourdough discard sneaks in a tiny tang that keeps every bite from tasting flat, and pure vanilla extract makes the whole pan smell ridiculous.

Thick buttercream on top? Yes, I want the corner piece with extra frosting and a stupid amount of sprinkles.

But the real win is the texture: soft middle, buttery edges, sweet bite after sweet bite. And for Valentine’s Day, I’ll take bars over cutouts every single time.

No contest.

Ingredients

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All-purpose flour gives these bars their soft, cookie-cake kind of bite.
Baking powder helps them puff a little, so they’re not too dense.
Baking soda keeps the texture tender and helps with that light golden edge.
Fine salt makes the vanilla and butter taste louder, in the best way.
Soft butter brings that rich, classic sugar cookie flavor we all want.
Granulated sugar keeps things sweet, simple, and lightly crisp around the edges.
Brown sugar adds a little chew and cozy caramel flavor.
The egg holds everything together and gives the bars structure.
Sourdough discard adds tang, moisture, and a little “what is that?” magic.
Vanilla extract is the main character here, sweet and warm.
Milk or cream helps the dough behave if it’s feeling too thick.
Powdered sugar makes the buttercream smooth, fluffy, and bakery-style.
Plus, butter in the frosting makes every bite feel extra special.
Basically, sprinkles make them cuter and way more fun to share.

Ingredient Quantities

2 1/2 cups all purpose flour

1 teaspoon baking powder

1/2 teaspoon baking soda

1/2 teaspoon fine salt

1 cup unsalted butter, softened (2 sticks)

1 cup granulated sugar

1/2 cup packed light brown sugar

1 large egg

1 cup active sourdough discard (100 percent hydration)

1 tablespoon pure vanilla extract

2 tablespoons milk or cream (as needed for dough)

2 cups powdered sugar (for buttercream)

4 tablespoons unsalted butter, softened (for buttercream)

1 to 2 tablespoons milk or cream (for buttercream)

1 teaspoon vanilla extract (for buttercream)

Pinch of salt (for buttercream)

Optional: sprinkles or sanding sugar for topping

How to Make this

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1. Preheat oven to 350°F (175°C) and line a 9×13 inch baking pan with parchment, leaving an overhang for easy removal.

2. In a bowl whisk together 2 1/2 cups all purpose flour, 1 teaspoon baking powder, 1/2 teaspoon baking soda, and 1/2 teaspoon fine salt; set aside.

3. In a large bowl cream 1 cup softened unsalted butter with 1 cup granulated sugar and 1/2 cup packed light brown sugar until light and fluffy.

4. Add 1 large egg, 1 cup active sourdough discard (100 percent hydration), and 1 tablespoon pure vanilla extract to the creamed mixture and beat until smooth.

5. Gradually add the dry ingredients to the wet mixture and stir until just combined; if the dough seems too stiff, add up to 2 tablespoons milk or cream to reach a soft, spreadable bar dough.

6. Press the dough evenly into the prepared pan, smoothing the top with a spatula or your fingers.

7. Bake for 20 to 25 minutes until the edges are lightly golden and the center is set but still soft; remove from oven and cool completely in the pan on a wire rack.

8. For the buttercream, beat 4 tablespoons softened unsalted butter until creamy, then gradually add 2 cups powdered sugar, 1 teaspoon vanilla extract, a pinch of salt, and 1 to 2 tablespoons milk or cream until smooth and spreadable.

9. Spread the buttercream over the cooled bars, garnish with optional sprinkles or sanding sugar, use the parchment overhang to lift the slab from the pan, slice into bars, and serve.

Equipment Needed

1. 9×13 inch baking pan and parchment paper (with overhang)
2. Mixing bowls (one large, one medium)
3. Electric hand mixer or stand mixer
4. Whisk and wooden spoon or silicone spatula
5. Measuring cups and spoons
6. Offset spatula or flat spatula for spreading
7. Wire cooling rack
8. Knife or bench scraper for slicing bars

FAQ

What is active sourdough discard and can I use refrigerated discard? Active discard means it has been recently fed and is bubbly; it gives lift and tang. You can use refrigerated discard but let it come to room temperature and, if possible, feed and wait until bubbly for best texture.

My dough seems too wet or too dry, how much milk or cream should I add? Start with 1 tablespoon and add up to 2 tablespoons total only if needed. Dough should be soft but not sticky; if too wet, add a tablespoon of flour at a time until manageable.

Can I skip the buttercream or replace it with something lighter? Yes. The bars are delicious plain or dusted with powdered sugar. For a lighter option, spread a thin glaze made from powdered sugar and milk or use a yogurt-based frosting, adjusting sweetness to taste.

How should I store these bars and how long do they keep? Store in an airtight container at room temperature for up to 3 days or in the refrigerator for up to 7 days. For longer storage, freeze unglazed bars for up to 2 months and thaw before frosting.

Can I make the dough or buttercream ahead of time? Yes. Dough can be wrapped and refrigerated for 24 hours or frozen for up to 1 month. Buttercream can be refrigerated for up to 5 days or frozen for 1 month; bring to room temperature and rewhip before using.

Do I need to adjust baking time or temperature if I use a different pan size? Yes. Thicker layers in a smaller pan require extra baking time; thinner layers bake faster. Check doneness with a lightly browned top and a toothpick that comes out with a few moist crumbs. Start checking 5 to 7 minutes earlier than the recipe time if using a larger or shallower pan.

Vanilla Sourdough Sugar Cookie Bars Recipe Substitutions and Variations

All purpose flour
- 1-to-1 gluten free flour blend (with xanthan gum) in equal measure for a gluten free version
- Whole wheat pastry flour, replace up to 50% for nuttier flavor and slightly denser texture
- Cake flour for a lighter, more tender crumb; use slightly more gently leveled by weight if possible
Active sourdough discard (100% hydration)
- Buttermilk, 1 cup, gives similar tang and hydration
- Plain yogurt thinned with a little milk to match the consistency, 1 cup total
- Sourdough starter fed and active, use 1 cup but reduce added liquid slightly
Unsalted butter (dough)
- Coconut oil, solid, 1:1 swap; imparts mild coconut flavor
- Margarine or stick vegan butter, 1:1 for dairy free option
- Vegetable shortening, 1:1 for extra tender, less spread
Powdered sugar (for buttercream)
- Make your own: blend granulated sugar with 1 to 2 tablespoons cornstarch per cup until powdered, then sift
- Use a simple glaze of sifted granulated sugar dissolved in milk or cream and vanilla for a lighter topping
- Cream cheese frosting in place of buttercream for tang and richness; adjust sweetness to taste

Pro Tips

1. Let the discard come to room temperature before mixing so it blends smoothly into the batter and you avoid overworking the dough. If your discard is very tangy, taste and adjust the sugar slightly to keep the balance you like.

2. Spoon and level your flour rather than scooping from the bag to prevent a dense, dry bar. If the dough looks tight after folding in the flour, add the milk a teaspoon at a time until it spreads easily without becoming runny.

3. Bake until the center is just set and the edges are lightly golden. The bars will continue to firm up as they cool, so err on the side of a few minutes less rather than more to keep them tender.

4. For silky buttercream, beat the butter until completely smooth before adding powdered sugar, and add milk a little at a time until you reach a spreadable consistency. If tiny air pockets appear while spreading, chill the frosting briefly, then smooth with a warm offset spatula for a clean finish.

Vanilla Sourdough Sugar Cookie Bars Recipe

Recipe by Kate Sinclair

0.0 from 0 votes

Servings

servings

Calories

245

kcal

Equipment: 1. 9×13 inch baking pan and parchment paper (with overhang)
2. Mixing bowls (one large, one medium)
3. Electric hand mixer or stand mixer
4. Whisk and wooden spoon or silicone spatula
5. Measuring cups and spoons
6. Offset spatula or flat spatula for spreading
7. Wire cooling rack
8. Knife or bench scraper for slicing bars

Ingredients

2 1/2 cups all purpose flour
1 teaspoon baking powder
1/2 teaspoon baking soda
1/2 teaspoon fine salt
1 cup unsalted butter, softened (2 sticks)
1 cup granulated sugar
1/2 cup packed light brown sugar
1 large egg
1 cup active sourdough discard (100 percent hydration)
1 tablespoon pure vanilla extract
2 tablespoons milk or cream (as needed for dough)
2 cups powdered sugar (for buttercream)
4 tablespoons unsalted butter, softened (for buttercream)
1 to 2 tablespoons milk or cream (for buttercream)
1 teaspoon vanilla extract (for buttercream)
Pinch of salt (for buttercream)
Optional: sprinkles or sanding sugar for topping

Directions

Preheat oven to 350°F (175°C) and line a 9×13 inch baking pan with parchment, leaving an overhang for easy removal.
In a bowl whisk together 2 1/2 cups all purpose flour, 1 teaspoon baking powder, 1/2 teaspoon baking soda, and 1/2 teaspoon fine salt; set aside.
In a large bowl cream 1 cup softened unsalted butter with 1 cup granulated sugar and 1/2 cup packed light brown sugar until light and fluffy.
Add 1 large egg, 1 cup active sourdough discard (100 percent hydration), and 1 tablespoon pure vanilla extract to the creamed mixture and beat until smooth.
Gradually add the dry ingredients to the wet mixture and stir until just combined; if the dough seems too stiff, add up to 2 tablespoons milk or cream to reach a soft, spreadable bar dough.
Press the dough evenly into the prepared pan, smoothing the top with a spatula or your fingers.
Bake for 20 to 25 minutes until the edges are lightly golden and the center is set but still soft; remove from oven and cool completely in the pan on a wire rack.
For the buttercream, beat 4 tablespoons softened unsalted butter until creamy, then gradually add 2 cups powdered sugar, 1 teaspoon vanilla extract, a pinch of salt, and 1 to 2 tablespoons milk or cream until smooth and spreadable.
Spread the buttercream over the cooled bars, garnish with optional sprinkles or sanding sugar, use the parchment overhang to lift the slab from the pan, slice into bars, and serve.

Notes

Below you’ll find my best estimate of this recipe’s nutrition facts. Treat the numbers as a guide rather than a rule—great food should nourish both body and spirit. Figures are approximate, and the website owner assumes no liability for any inaccuracies in this recipe.