Begin by preheating your oven to 350 degrees F and oiling a 9x13 baking dishIn a medium sized mixing bowl cream together1/2 Cup softened butter1/2 Cup white sugarand1/4 Cup + 1 Tbs brown sugar
Blend in 1 Room temperature eggand 1 tsp vanilla extractMix until just combined, being careful not to over mix
In a separate bowl combine1 1/2 Cups all purpose flour1 tsp baking powder1/2 tsp baking soda1/2 tsp cornstarch1/4 tsp saltGently add it into the wet ingredients while mixing
Press the dough firmly into the greased 9x13 baking dish, making sure it is even out to the edgesSprinkle 1 Cup white chocolate chips on top and gently press them down into the dough
Bake for 17-22 minutes until the edges are slightly brownedOver the top sprinkle3 Cups mini marshmallows1/4 Cup caramel M&Ms1/4 Cup dark chocolate M&Ms1/4 Cup white chocolate M&Msand3 Tbs pastel colored sprinkles
Bake for an additional 3 minutes until the marshmallows are slightly puffyAdd more sprinkles white chocolate chipsAllow to cool completely before slicing and serving