Preheat oven to 350 degrees Fahrenheit. In a small saucepan, melt butter and oil on medium-low heat, stirring regularly. Once melted, add chocolate chips and whisk until smooth. Allow to cool slightly and transfer to your mixing bowl or stand mixer.

Add cane sugar, brown sugar, eggs, sourdough discard, and vanilla extract to the melted chocolate mixture. Stir until combined.

Next, add cacao or cocoa powder, flour, milk powder, salt, and cornstarch. Mix until combined and transfer to a parchment paper-lined 9x9 baking dish.

Bake uncovered for 30-35 minutes. Remove from the oven when the center is firm but jiggles slightly when you shake it. It will finish baking outside of the oven. This will result in a very fudgy brownie.