Step 1: Preheat your oven to 350°F (175°C). Line a 9×13 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal. Spray lightly with non-stick spray.
Step 2: Prepare the Brownie Layer: In a medium bowl, whisk together the melted butter and granulated sugar until well combined. Beat in the eggs one at a time, then stir in the vanilla extract.
Step 3: In a separate small bowl, whisk together the cocoa powder, flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Fold in the chocolate chips.
Step 4: Pour the brownie batter into the prepared baking pan and spread evenly. Set aside while you prepare the cookie layer.
Step 5: Prepare the Cookie Layer: In a large bowl, cream together the softened butter, granulated sugar, and brown sugar with an electric mixer until light and fluffy (about 2-3 minutes).
Step 6: Beat in the egg and vanilla extract until well combined.
Step 7: In a separate small bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Stir in the chocolate chips.
Step 8: Assemble and Bake: Drop spoonfuls of the cookie dough evenly over the brownie layer. Gently spread the cookie dough with an offset spatula or your hands, trying to cover as much of the brownie layer as possible. It doesn’t need to be perfect; a slightly rustic look is charming.
Step 9: Bake for 30-35 minutes, or until the cookie layer is golden brown and a toothpick inserted into the center of the brownie layer comes out with moist crumbs (not wet batter). Be careful not to overbake, as this can make the brookies dry.
Step 10: Let the brookies cool completely in the pan on a wire rack before lifting them out using the parchment paper overhang. This is crucial for clean cuts. Once cooled, slice into squares and serve. Enjoy your homemade brookies!