Preheat your oven to 350 degrees and line a large 11x17 inch cookie sheet with parchment paper.
Add sugars, semi sweet chocolate, and milk to a large microwavable bowl. Microwave for 1-2 minutes until chocolate is melted and smooth. Stir to combine and set aside to cool.
In a separate large prep bowl add flour, unsweetened cocoa powder, baking powder and salt and whisk or sift. Set aside.
Once cooled, add eggs, oil, and vanilla extract to the melted sugar and chocolate. Stir until well combined.
Fold the dry ingredients into the wet ingredients and stir until just combined and no flour remains visible.
Pour the brownie batter onto the cookie sheet and smooth into an even, thin layer. Top with chocolate chips and nuts if using.
Bake on the center rack for 30-40 minutes or until the top is firm. Rotate the pan halfway through.
Once baked, remove from over and let cool. Once cooled, break or cut the brownie brittle apart and enjoy.
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