Preheat oven to 350 °F. Lightly grease an 8 x 8 baking mold and line with wax paper. Grease once again. In a water bath, melt 3 tablespoons of coconut oil with the chocolate chips. In a bowl, combine ground Cheerios™, potato starch, salt and baking powder. In a separate bowl, use a whisk to combine the rest of the coconut oil with the 2 types of sugar, then add the eggs, one by one, and vanilla extract. Incorporate Cheerios™ mixture. Divide the dough into 2 equal parts. Add melted chocolate to one and peanut butter to the other. Add the peanut butter dough to the mold and then add the chocolate dough. Bake for 35 minutes or until a toothpick inserted in the middle of the brownie comes out with just a few damp pieces. Remove from oven and let cool. Cut into 16 squares, garnish with dulce de leche and a few chocolate chips. Serve.