Preheat your oven to 350°F (176°C). Line a 9"x9" baking dish with parchment paper.
Melt the butter in a small saucepan over low heat. Add chocolate chips, vanilla extract, and cocoa powder to the melted butter. Stir until smooth and remove from heat to cool slightly.
In a large mixing bowl, beat the eggs, brown sugar, and granulated sugar until light and creamy. Add the sourdough discard and cooled chocolate mixture, and beat until well combined. Gently fold in the flour and salt until just incorporated.
Pour the batter into the lined baking dish and smooth the top. Bake for 35-40 minutes or until a toothpick inserted in the center comes out with a few moist crumbs.
Allow the brownies to cool completely in the pan. Lift them out using the parchment paper and slice into squares.
