# What You'll Need:
→ Chocolate & Cocoa
01 - 4 oz bittersweet chocolate, chopped
02 - 2 oz milk chocolate, chopped
03 - 1/4 cup unsweetened Dutch-process cocoa powder
→ Fats
04 - 1/2 cup unsalted butter, cubed
→ Sugar
05 - 1 cup granulated sugar
06 - 1/4 cup light brown sugar, packed
→ Sourdough & Liquids
07 - 1/2 cup sourdough discard, unfed
08 - 2 large eggs, at room temperature
09 - 1 teaspoon pure vanilla extract
→ Dry Ingredients
10 - 2/3 cup all-purpose flour
11 - 1/2 teaspoon fine sea salt
→ Chocolate Mix-ins
12 - 1/3 cup semi-sweet chocolate chips or chunks
# Steps to Follow:
01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, leaving overhang for easy removal.
02 - In a heatproof bowl, combine bittersweet chocolate, milk chocolate, cocoa powder, and butter. Melt over simmering water or in microwave using 30-second bursts, stirring until smooth. Cool slightly.
03 - In a large bowl, whisk together sugars, eggs, and vanilla extract until pale and thick, approximately 2 to 3 minutes.
04 - Whisk sourdough discard into the chocolate mixture until fully incorporated.
05 - Add chocolate mixture to egg-sugar mixture and mix gently until combined.
06 - Sift in flour and salt. Fold in gently with a spatula until just combined; do not overmix.
07 - Gently fold chocolate chips or chunks into the batter.
08 - Pour batter into prepared pan and smooth the top evenly.
09 - Bake for 28 to 32 minutes, or until edges are set and center is just slightly wobbly. Do not overbake to maintain chewy center.
10 - Cool completely in the pan on a wire rack before lifting out and slicing into squares.