Preheat your oven to 350°F (175°C) and prepare an 8x8-inch baking dish by greasing it or lining it with parchment paper.

Melt 1/2 cup of unsalted butter in a medium saucepan over low heat until it’s completely liquid and warm, but not boiling.

Combine the melted butter with granulated sugar, eggs, and vanilla extract in the saucepan. Stir until well mixed, then add cocoa powder, flour, salt, and baking powder.

Spread the brownie batter evenly in the prepared baking dish and bake for 20–25 minutes. Let the brownies cool in the pan.

Cream together the softened butter, brown sugar, and granulated sugar in a mixing bowl using a hand mixer until light and fluffy.

Add vanilla extract and mix until fully incorporated.

Incorporate the flour and salt gradually into the mixture until just combined. If the dough seems too crumbly, add milk until the consistency is smooth.

Fold in mini chocolate chips gently into the dough.

Spread the cookie dough layer evenly over the cooled brownie base.

Refrigerate the brownies for about 30 minutes to firm up the cookie dough layer.

Cut the brownies into squares and serve to friends and family.