Preheat oven to 325°F. In a large bowl, mix together ½ cup melted peanut butter, 1 cup sugar, 2 eggs, 1 tsp baking powder, ½ cup flour, and ½ cup cocoa powder. Pour the batter in a baking tray. Put 6 tsp of creamy peanut butter, and mix slightly. Then, bake for 20-25 minutes. Cool, cut, and serve!