Beat 1/2 cup of softened butter, 1/2 cup of light brown sugar, 1/4 cup of white sugar, and 1/2 teaspoon of vanilla extract together in a large bowl until creamy. Add 1 egg; beat until light and creamy, about 2 minutes.
Whisk 1-1/4 cups of flour, 1/2 teaspoon of salt, and baking soda together in a bowl. Slowly stir flour mixture into butter mixture until dough is combined. Stir chocolate chips into dough. Spread dough into the bottom of a muffin pan, 1/4 inch layer.
Stir 1 cup of white sugar, melted butter, and 1 teaspoon of vanilla extract together in a bowl. Add 2 eggs and beat well. Mix cocoa powder into butter mixture until well combined. Stir 1/2 cup flour, 1/4 teaspoon baking powder, and 1/8 teaspoon salt into cocoa mixture until batter is combined. Add 2 tablespoons of brownie batter over the cookie dough. Spread to even out.
Bake in preheated oven for 20-25 minutes.
Immediately after removing from oven, press a circular object in the middle of each brookie to form the bowl.