If brownies are about deep dark cocoa, blondies are all about the magic of caramelized brown butter, dark brown sugar, and pure vanilla. These brown butter sourdough discard blondies take things a step further: the subtle fermented tang of sourdough discard cuts through the richness of nutty browned butter, creating an intensely chewy, butterscotch-flavored bar cookie that is impossible to resist.
No stand mixer is required—this one-bowl recipe comes together with a wooden spoon and bakes in under 30 minutes.
Why Brown Butter and Sourdough Discard are Soulmates
- The Brown Butter Alchemy: Melting butter until the milk solids turn golden amber and smell nutty adds a deeply toasted, toffee-like complexity that ordinary melted butter cannot match.
- Chewy, Never Cakey: Using only baking soda (no baking powder) and keeping the flour ratio low ensures the blondies remain dense, chewy, and gooey in the center.
- Sourdough Balances Sweetness: Traditional blondies can sometimes taste cloyingly sweet. The gentle lactic acid in sourdough discard balances the brown sugar perfectly.
Ingredients (Grams & Cups)
- Unsalted Butter (115g / 1/2 cup): Browned on the stovetop.
- Dark Brown Sugar (150g / 3/4 cup, packed): Essential for that chewy toffee texture.
- Granulated White Sugar (50g / 1/4 cup): Helps create a shiny top crust.
- Sourdough Discard (120g / 1/2 cup): 100% hydration, unfed.
- Large Egg (1 room temperature) & Pure Vanilla Extract (2 tsp).
- All-Purpose Flour (140g / 1 cup + 2 tbsp): Spooned and leveled.
- Baking Soda (1/2 tsp) & Fine Sea Salt (1/2 tsp).
- Mix-ins (100g / approx. 3/4 cup): Chopped white chocolate, butterscotch chips, or toasted pecans.
- Flaky Sea Salt (Maldon): For sprinkling over the top!
Step-by-Step Blondie Method
- Brown the Butter: Melt butter in a light-colored saucepan over medium heat. Swirl occasionally as it foams and sizzles. After 4–5 minutes, you will see golden-brown specks at the bottom and a nutty aroma. Immediately remove from heat and pour into a mixing bowl to prevent burning. Cool for 5 minutes.
- Mix Wet: Whisk brown sugar, white sugar, egg, vanilla extract, and sourdough discard into the warm brown butter until glossy and fully emulsified.
- Fold Dry & Add Mix-ins: Stir in flour, baking soda, and fine salt with a rubber spatula just until no dry flour remains. Fold in chocolate chunks or pecans.
- Bake: Spread batter into an 8×8-inch parchment-lined metal pan. Bake at 350°F (175°C) for 24 to 28 minutes. The edges should be golden and pulling away from the sides, but the center should still be soft and slightly jiggly.
- Salt & Cool: Sprinkle flaky sea salt immediately. Cool completely in the pan for at least 1 hour before slicing into 16 chewy squares.
🥖 Free Sourdough Troubleshooting Guide
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Brown Butter Sourdough Discard Blondies
Ultra-chewy butterscotch bar cookies made with nutty brown butter, sourdough starter discard, and flaky sea salt.
Ingredients:
- 115g unsalted butter (1/2 cup), browned
- 150g dark brown sugar (3/4 cup)
- 50g granulated sugar (1/4 cup)
- 120g sourdough discard (1/2 cup)
- 1 large egg
- 2 tsp pure vanilla extract
- 140g all-purpose flour (1 cup + 2 tbsp)
- 1/2 tsp baking soda
- 1/2 tsp fine sea salt
- 100g white chocolate or butterscotch chips
- Flaky sea salt for topping
Instructions:
- Brown butter in saucepan until nutty and golden; cool 5 minutes.
- Whisk sugars, egg, vanilla, and discard into the warm butter.
- Fold in flour, baking soda, salt, and mix-ins until just combined.
- Spread into 8×8 pan and bake at 350°F (175°C) for 24 to 28 minutes.
- Top with flaky sea salt and cool completely before cutting into 16 squares.
More Decadent Discard Treats
If you love bar cookies and brownies, be sure to make our fudgy sourdough discard brownies and our chewy chocolate chip cookies.