Preheat the oven to 350F. Line a 9 x 13 baking pan with parchment paper, leaving some overhang.
Start the brownies. Melt your butter and add the granulated and brown sugar as well as the vanilla extract to the butter and whisk well.
Whisk in the eggs and beat well for 2 - 3 minutes.
Mix together the flour, salt, baking powder and cocoa powder and stir into the butter mixture. Pour into the lined baking pan and spread evenly along the bottom.
Beat the butter, the granulated and brown sugar, and vanilla together using a stand mixer until light and fluffy, about 3 - 4 minutes.
Add in the egg and beat well until well combined, at least another minute.
Mix together the flour, baking powder, and salt together and add to the butter. Mix until just combined, then fold in most of the chocolate.
Dollop the cookie dough over the brownie mixture and then spread. Top with any remaining chocolate.
Bake the brownies for 30 - 35 minutes, or until a toothpick inserted in the center comes out with very thick brownie batter or moist crumbs.
Serve at room temperature with a few scoops of ice cream!
Notes
Make sure all the ingredients are at room temperature. Cut the butter in small pieces to encourage it to soften quickly. You can also leave the eggs in a bowl of warm water for five minutes to quickly warm them. Fluff up the flour and spoon it into your measuring cups and sweep off the excess to prevent adding too much flour. Use a kitchen scale for accuracy. Wait until the brookies completely reach room temperature before attempting to remove them from the pan. Doing it while they are still warm will result in them breaking apart as you lift the parchment paper.