Fluffy Vanilla Cake with Whipped Vanilla Bean Frosting {William's 1st Birthday!}

INGREDIENTS

large egg whites (150g), at room temperature

whole egg, at room temperature

1 cup

whole milk, at room temperature

2 1/4 tsp

pure vanilla extract

3 cups

cake flour, sifted

2 cups

sugar

1 tbsp

plus 1 tsp (17g) baking powder

3/4 tsp

salt

12 tbsp

unsalted butter, cold and cut into 24 pieces

3 sticks

plus 2 tbsp. (375g) unsalted butter, cut into cubes and softened

3 tbsp

milk

Seeds scraped from one vanilla bean

1 tsp

pure vanilla extract

salt

3 cups

sifted (475g) confectioners' sugar