Preheat the Oven: Preheat your oven to 350°F (175°C). Line a 9×13-inch (23×33 cm) baking pan with parchment paper or lightly grease it.

Prepare the Brownie Batter:

• In a large bowl, whisk together the melted butter and granulated sugar until well combined.
• Add the eggs and vanilla extract, whisking until smooth.
• Sift in the flour, cocoa powder, salt, and baking powder. Stir until just combined; avoid overmixing.
• Pour the brownie batter into the prepared baking pan, spreading it evenly.

Prepare the Cookie Dough:

• In a separate bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
• Beat in the egg and vanilla extract until well incorporated.
• In another bowl, whisk together the flour, baking powder, and salt. Gradually add this to the wet mixture, mixing until combined.
• Fold in the semi-sweet chocolate chips.

Assemble the Brookies:

• Drop spoonfuls of the cookie dough over the brownie batter in the pan. Gently spread and press the dough to create an even layer over the brownie batter.

Bake:

• Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. The top should be golden brown, and the edges set.

Cool and Serve:

• Allow the brookies to cool completely in the pan on a wire rack. Once cooled, cut into squares and serve;