Begin by melting half of your butter and softening the other half. In a large mixing bowl, cream together the melted and softened butter with the brown and granulated sugars until light and fluffy, about 3–5 minutes. Incorporate the eggs one at a time, mixing well before adding the next, and finish mixing in the vanilla extract.

In a separate bowl, whisk together the all-purpose flour, cornstarch, baking soda, and salt until no lumps remain. Gradually add this dry mixture to the wet ingredients, stirring gently until just combined.

Fold in the chocolate chips gently to combine them evenly throughout the dough.

Chill the dough in the refrigerator for at least 2 hours to help prevent spreading during baking.

Prepare your brownies according to your favorite recipe, baking them until slightly underbaked. Allow to cool before chopping into small chunks.

Scoop about two tablespoons of cookie dough, flatten it, place a brownie chunk in the center, and encase it with the dough. Repeat until all dough and brownie pieces are used.

Bake at 350°F for 11 minutes or until the edges are lightly golden and centers look slightly underbaked. Cool on the baking sheet for a few minutes before transferring to a wire rack.