Sourdough Cosmic Chocolate Brownies (Printable)

Fudgy, tangy sourdough chocolate brownies studded with chips and rainbow sprinkles; bake 28–32 minutes.

# What You’ll Need:

→ Wet Ingredients

01 - 1/2 cup unsalted butter, melted
02 - 7 oz dark chocolate (70% cacao), chopped
03 - 3/4 cup granulated sugar
04 - 1/4 cup plus 2 tbsp light brown sugar, packed
05 - 2 large eggs, room temperature
06 - 1 tsp pure vanilla extract
07 - 1/2 cup active sourdough starter (100% hydration, unfed or discard)

→ Dry Ingredients

08 - 2/3 cup all-purpose flour
09 - 1/4 cup unsweetened cocoa powder
10 - 1/2 tsp fine sea salt

→ Cosmic Topping

11 - 3/4 cup mini chocolate chips or candy-coated chocolate pieces
12 - 3 tbsp rainbow sprinkles

# Steps:

01 - Preheat oven to 350°F. Line an 8x8 inch baking pan with parchment paper, leaving an overhang on two sides for easy removal.
02 - Place the unsalted butter and chopped dark chocolate in a heatproof bowl. Set over a pot of barely simmering water (double boiler) or microwave in 30-second intervals, stirring between each, until completely smooth. Let cool for 5 minutes.
03 - Add granulated sugar and brown sugar to the chocolate mixture, whisking until glossy and well blended. Beat in eggs one at a time, whisking thoroughly after each addition. Stir in vanilla extract.
04 - Fold the sourdough starter into the batter using a spatula, mixing until fully incorporated with no visible streaks.
05 - Sift flour, cocoa powder, and salt directly into the bowl. Gently fold the dry mixture into the wet batter until just combined. Avoid overmixing to keep the texture tender.
06 - Pour the batter into the prepared pan and spread evenly with a spatula. Scatter mini chocolate chips or candy-coated pieces over the surface, then generously sprinkle rainbow sprinkles on top.
07 - Bake for 28 to 32 minutes, or until a toothpick inserted in the center comes out with moist crumbs clinging to it. Avoid overbaking for the fudgiest result.
08 - Let the brownies cool completely in the pan set on a wire rack. Once fully cooled, use the parchment overhang to lift the slab out and cut into 16 squares.

# Expert Advice:

01 -
  • The sourdough starter adds a subtle tang that makes the chocolate taste deeper and more interesting without anyone guessing your trick.
  • That cosmic sprinkle topping turns an already incredible brownie into something that makes people smile before they even take a bite.
  • You finally have a legitimate reason to keep your sourdough discard instead of guiltily throwing it away every week.
02 -
  • Pulling the brownies out on the earlier side of the bake window gives you that dense, gooey center everyone fights over.
  • If you do not have sourdough starter handy, 100 g of plain Greek yogurt will give you a similar tang in a pinch.
03 -
  • Weigh your ingredients with a kitchen scale rather than using measuring cups, because even a small excess of flour turns fudgy brownies into cakey disappointments.
  • Let the melted chocolate cool for at least five minutes before adding eggs, unless you enjoy the texture of accidental chocolate scrambled eggs.

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