Preheat the oven to 350 degrees F. Line an 8 x 8 or 9 x 9 inch square baking dish with parchment paper and set aside.
In a large bowl, whisk together the sugar, flour, cocoa powder, salt, and baking powder. Make a well (hole) in the center and drop in the butter, eggs, and vanilla extract. Mix together thoroughly and then fold in the chocolate chips with a rubber spatula. Spread in one even layer on the bottom of the parchment-lined baking dish.
Peanut Butter Layer
In another large bowl, mix together everything except the chocolate chips until thoroughly combined. Fold in the chocolate chips.
Carefully spread on top of the brownie layer in the baking dish. I find it's best to drop clumps in various locations on top of the brownie batter to help get an even spread without mixing the two together.
Bake until golden brown on top, about 30 to 35 minutes. Let cool. Holding the parchment paper, lift out of the pan. Cut into squares and enjoy!