Yellow Layer Cake with Creamy Chocolate Frosting

Ingredients

• 2½ cups cake flour, plus extra for dusting pans
• 1¼ teaspoons baking powder
• ¼ teaspoon baking soda
• ¾ teaspoon table salt
• 1¾ cups sugar (12¼ ounces)
• 10 tablespoons (1¼ sticks) unsalted butter, melted and cooled slightly
• 1 cup buttermilk, room temperature
• 3 tablespoons vegetable oil
• 2 teaspoons vanilla extract
• 6 large egg yolks, room temperature
• 3 large egg whites, room temperature
• 8 tablespoons (1 stick) butter, room temperature
• 3 cups confectioner’s sugar, sifted
• ½ cup unsweetened cocoa powder, sifted
• 3 to 5 tablespoons milk
• 1 teaspoon pure vanilla extract