The most extraordinary half-brownie-half-cookie Brookies made by preheating oven to 350°F greasing and lining 9×13 pan preparing 1 box brownie mix according to box directions pouring into pan spreading evenly pre-baking at 350°F exactly 10 minutes until surface slightly set but still wet while brownie pre-bakes whisking 1 1/2 cups flour 1/2 tsp baking soda and 1/2 tsp salt beating 1/2 cup softened butter 1/2 cup packed brown sugar and 1/4 cup granulated sugar 2 minutes light and fluffy adding 1 room temperature egg and 1 tsp vanilla mixing combined adding flour mixture just combined folding 1 cup chocolate chips dropping generous spoonfuls over pre-baked brownie surface spreading gently with dampened hands or floured spatula returning to oven baking additional 20 to 25 minutes until cookie layer gorgeously golden and toothpick shows few moist crumbs cooling completely minimum 1 full hour before cutting. A completely perfect fudgy brownie chocolate chip cookie layered brookie bar recipe.