Heat oven to 350-degrees. Line an 8-inch square pan with foil, letting ends extend above the pan on two sides. Spray foil in pan with nonstick cooking spray. Mix cocoa, sugars, flour and baking powder in a large bowl. Add egg whites, egg, oil and vanilla and mix until blended.

Stir in 1/2-cup each of the marshmallows and broken crackers. Spread batter evenly in prepared pan. Bake ten minutes. Sprinkle remaining marshmallows and graham crackers over top, pressing them gently until partially submerged in batter. Bake 18 to 20 minutes longer until marshmallows on top are golden brown. Cool completely in pan on a wire rack. Lift foil by ends to a cutting board. Peel off foil and cut into squares.