Preheat oven to 350F and grease a 9×9 baking dish. Set aside.
In a saucepan over medium-low heat, melt the butter, add in the chocolate chips, and stir until melted. Mix in the cocoa powder and vanilla extract. Once melted, set aside and allow to cool down.
In a standing or handheld mixer, mix together the sugars and eggs for 10 minutes to create the meringue. Add in the sourdough discard and the chocolate and mix together. Fold in the flour and salt until just incorporated.
Pour the mixture into the prepared baking dish and bake for 45-50 minutes. Poke the center with a toothpick at 45 minutes. If a lot of batter comes up with the toothpick, bake for an additional 5 minutes.
Remove brownies from oven and allow to completely cool.