Perfect Yellow Cake

INGREDIENTS

• 2 sticks (1 cup) butter
• 2 cups sugar
• 4 eggs
• 2 2/3 cups sifted cake flour
• 2 teaspoons baking powder
• 1/2 teaspoon salt
• 1 cup milk
• 1 1/2 teaspoons vanilla
• 1/2 cup unsalted butter
• 5 tablespoons cocoa powder
• 1/2 cup milk
• 16 ounces (1 box) powdered sugar
• 1 teaspoon vanilla