Preheat your oven to 350°F (175°C) and grease a baking pan.

Melt the unsalted butter in a saucepan over low heat, remove from heat, and mix in cocoa powder, granulated sugar, and salt.

Incorporate eggs and vanilla extract, then gradually fold in the all-purpose flour and baking powder.

In a mixing bowl, cream together softened butter and brown sugar until fluffy, then add eggs and vanilla extract.

Blend in all-purpose flour, baking powder, and pinch of salt until cookie dough forms, then stir in chocolate chips.

Spread half of the brownie batter in the baking pan and dollop cookie dough on top, spreading it evenly.

Pour remaining brownie batter on top of the cookie layer and smooth it down.

Bake for 30-35 minutes, checking for doneness with a toothpick.

Cool for at least 20 minutes before cutting into squares.

Serve warm or let cool completely before storing.