– 3/4 c. (1 1/2 sticks) butter, room temperature – 1 c. granulated sugar – 1 egg + 1 egg yolk – 1 1/2 tsp. vanilla – 2 1/4 c. all-purpose flour – 1 tsp. baking powder – 1/4 tsp. salt – 1/3 c. rainbow sprinkles, plus additional for topping – 1/2 c. semi-sweet chocolate chips – 1/2 c. white chocolate chips Frosting: – 1/2 c.(1 stick) butter, room temperature – 1 tsp. vanilla – 3 c. powdered sugar – 2-3 Tbsp. milk – Gel food coloring (color of your choosing)