Step 1: Prepare the Oven
Preheat oven to 350°F (176°C).
Line a 9×9-inch baking dish with parchment paper.
Step 2: Melt the Chocolate Mixture
Melt butter over low heat.
Add chocolate chips, cocoa powder, and vanilla.
Stir until smooth, then let it cool slightly.
Step 3: Make the Batter
In a large bowl:
Beat eggs, egg yolk, and sugars for 7–10 minutes until light and creamy
Mix in sourdough discard and melted chocolate
Fold in flour and salt gently
The batter will be thick.
Step 4: Bake
Pour batter into the pan and smooth the top.
Bake for 35–40 minutes until a toothpick shows moist crumbs.
Step 5: Cool & Serve
Let brownies cool completely.
Lift using parchment paper, slice, and serve.