Preheat your oven to 350°F (175°C) and line an 8×8 or 9×9-inch baking pan with parchment paper.

In a mixing bowl, whisk together melted butter and granulated sugar until glossy. Add eggs and vanilla extract, mixing until smooth.

Stir in cocoa powder, flour, and salt until just combined. Fold in chocolate chips if desired and pour the brownie batter into the prepared pan.

In a separate bowl, cream together softened butter, granulated sugar, and brown sugar until light and fluffy. Add egg and vanilla, mixing until incorporated.

Gradually stir in flour, baking soda, and salt until a dough forms. Fold in more chocolate chips and scoop the cookie dough onto the brownie layer.

Bake for 28-35 minutes until edges are set and center is slightly soft; a toothpick should come out with moist crumbs.

Cool completely in the pan on a wire rack. Once cooled, lift out using parchment paper and slice into squares.