# What You'll Need:
→ Chocolate & Cocoa
01 - 3.5 oz bittersweet chocolate (60–70% cacao), chopped
02 - 1.75 oz milk chocolate, chopped
03 - 1.75 oz white chocolate, chopped
04 - 1/4 cup unsweetened cocoa powder
→ Sourdough & Wet Ingredients
05 - 1/2 cup sourdough starter (100% hydration, unfed or discard)
06 - 1/2 cup unsalted butter, cubed
07 - 2 large eggs
08 - 1 tsp vanilla extract
09 - 2 tbsp strong brewed espresso or 1 tbsp instant espresso powder dissolved in 2 tbsp hot water
→ Dry Ingredients
10 - 3/4 cup granulated sugar
11 - 1/4 cup light brown sugar, packed
12 - 3/4 cup all-purpose flour
13 - 1/2 tsp fine sea salt
# Steps:
01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, leaving overhang for easy removal.
02 - In a heatproof bowl, combine bittersweet chocolate and butter. Melt over a double boiler using gently simmering water, stirring until smooth. Remove from heat and cool slightly.
03 - Whisk both sugars into the melted chocolate mixture until combined. Add eggs one at a time, whisking thoroughly after each addition. Stir in vanilla extract and espresso.
04 - Fold sourdough starter into the wet mixture until fully incorporated.
05 - Sift together flour, cocoa powder, and salt. Gently fold dry ingredients into the wet mixture until just combined. Avoid overmixing.
06 - Fold milk chocolate and white chocolate pieces into the batter.
07 - Pour batter into the prepared pan and smooth the top.
08 - Bake for 32–36 minutes until the center is just set and a toothpick inserted comes out with moist crumbs.
09 - Cool completely in the pan before lifting out and cutting into 12 equal squares.