Prepare the Oven: Preheat the oven to 350°F.
Prepare the Pan: Line a 9 × 9-inch square baking pan with parchment paper, or grease it thoroughly with butter.
Melt the Butter: Place the butter in a large microwave-safe bowl and melt it in the microwave.
Combine Butter Sugar: Stir the sugar into the melted butter until incorporated.
Add Cocoa Spices: Stir in the unsweetened cocoa powder, cayenne pepper, cinnamon, and kosher salt.
Add Eggs Vanilla: Add the eggs and vanilla extract, then mix well until the ingredients are thoroughly combined.
Add Flour Chocolate: Add the flour and semi-sweet chocolate chips, stirring only until the flour is just incorporated.
Fill the Pan: Spread the brownie batter evenly into the prepared baking pan.
Top with Chocolate: Sprinkle the milk chocolate chips evenly over the surface of the batter.
Bake the Brownies: Bake at 350°F for 25–30 minutes, or until a toothpick inserted into the center comes out with moist crumbs.
Cool in the Pan: Let the brownies cool in the pan for 5 minutes.
Cool Completely: Remove the brownies from the pan and transfer them to a wire rack to cool completely.
Slice and Serve: Once completely cool, cut the brownies into squares.