Preheat your oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper or lightly grease it with butter or nonstick spray to prevent the brownies from sticking.

In a large mixing bowl, whisk together the melted butter and sugar until smooth. Add the eggs one at a time, whisking well after each addition. Stir in the vanilla extract and sourdough discard until the mixture becomes fully combined.

Sift the cocoa powder, flour, and salt into the bowl. Gently fold the dry ingredients into the wet mixture using a spatula until just combined. Avoid overmixing, as this can make the brownies dense.

If you’re using chocolate chips, fold them into the batter. They will melt slightly during baking and create pockets of rich chocolate throughout the brownies.

Spread the brownie batter evenly into the prepared baking pan. Use a spatula to smooth the top so the brownies bake evenly.

Place the pan in the preheated oven and bake for 20–25 minutes, or until a toothpick inserted near the center comes out with a few moist crumbs.

Allow the brownies to cool completely in the pan before slicing. This helps them set properly and makes it easier to cut clean squares.