Heat oven to 350 degrees. Grease and line a 13-by-9-inch baking pan with parchment paper, leaving a 2-inch overhang on two sides.

Prepare the brownie layer: In a medium saucepan combine the butter and sugar, and heat over medium until the butter is melted. Remove from the heat and whisk vigorously until well combined.

Once the mixture has cooled a bit, whisk in the eggs one at a time. Whisk in the vanilla.

Add the flour, cocoa powder, baking powder and salt, and stir to combine. Transfer to a medium bowl.

Prepare the cookie batter: Wash and dry the saucepan. Combine the butter and sugar, and heat over medium until the butter is melted. Remove from the heat and whisk vigorously until well combined

Once the mixture has cooled a bit, whisk in the eggs one at a time. Whisk in the vanilla. Add the flour, baking powder and salt, and stir. Stir in ¾ cup of the chocolate.

Using two cookie scoops, drop each of the batters into the prepared pan. The pattern can be random, and one dough can be on top of the other; just make sure that once all the batter is added to the pan, you have an even thickness spread out across the pan. Sprinkle the remaining ½ cup chocolate on top.

Bake until the top looks dry and set, and a toothpick inserted into the center comes out with moist crumbs attached, 20 to 22 minutes.

Transfer to a rack to cool completely, about 45 minutes. Lift the bar out using the paper and transfer to a cutting board. Cut into bars to serve.