Hydrangea Cakes

granulated sugar (, (1 1/2 cups))

cake flour (, (2 2/3 cups))

+ 1 tsp baking powder

salt

egg whites (, (see Note below))

milk

vanilla extract

unsalted butter (, at room temperature)

Gel food coloring (, (I used Americolor electric purple, regal purple, sky blue, and soft pink))

pasteurized liquid egg whites (, (3/4 cup))

powdered sugar (, (6 cups))

salt

unsalted butter (, at room temperature)

vanilla extract

Gel food coloring (, (I used Americolor electric purple, regal purple, sky blue, and soft pink))