Prepare Your Oven and Baking Sheet: Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper.
Mix the Dry Ingredients: In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set aside.
Combine the Wet Ingredients: In a separate bowl, whisk together the granulated sugar, brown sugar, egg, and vanilla extract until smooth. Add the melted butter and stir until fully incorporated.
Make the Batter: Slowly incorporate the dry ingredients into the wet ingredients, mixing until just combined. Fold in the mini chocolate chips.
Spread and Bake: Pour the batter onto the lined baking sheet and use a spatula to spread it into a thin layer, about ¼ inch thick. Sprinkle additional chocolate chips or nuts on top if desired.
Bake to Perfection: Bake for 15-20 minutes, or until the edges are crispy and the center feels set. Watch closely in the last few minutes to avoid over-baking.
Cool and Break Apart: Allow the brownie brittle to cool completely on the baking sheet. Once cooled, break it into pieces of your desired size.