Preheat your oven to 350°F (175°C).

In a large bowl, cream together the softened butter, granulated sugar, and brown sugar. Beat in the eggs, one at a time, followed by the vanilla extract. Mix until well combined.

In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add this mixture to the wet ingredients, mixing gently until no dry bits remain. Fold in the chocolate chips.

In another bowl, melt the unsalted butter for the brownie layer. Stir in the sugar, eggs, and vanilla until smooth. Add in the cocoa powder, flour, baking powder, and salt, mixing until combined.

In a greased or lined baking dish, drop spoonfuls of cookie dough, followed by spoonfuls of brownie batter. Use a knife or skewer to swirl both batters together for a marbled effect.

Place the dish in your preheated oven and bake for about 25 minutes, or until a toothpick inserted in the center comes out with moist crumbs.

Allow the cookies to cool in the pan for 10 minutes before transferring them to a wire rack.

Enjoy the Brookie Cookies with a glass of cold milk or your favorite coffee.