Preheat your oven to 350°F (175°C). Grease or line an 8×8-inch baking pan with parchment paper.

In a medium saucepan, melt the butter over low heat. Remove from heat and whisk in the granulated sugar, brown sugar, cocoa powder, and salt until well combined.

Add the vanilla and eggs, one at a time, whisking vigorously after each addition until the batter is glossy.

Stir in the sourdough discard until fully incorporated.

Fold in the flour and chocolate chips until just combined—don’t overmix.

Pour the batter into your prepared pan and smooth out the top.

Bake for 25–30 minutes, or until the edges are set and a toothpick inserted into the center comes out with a few moist crumbs (not wet batter).

Let cool before slicing.