Yellow Sheet Cake with Chocolate Frosting | America's Test Kitchen

Ingredients

• 4 large eggs plus 2 large yolks
• 1/2 cup buttermilk
• 1 tablespoon vanilla extract
• 2 1/4 cups (9 ounces/255 grams) bleached cake flour
• 1 3/4 cups (12¼ ounces/347 grams) granulated sugar
• 1 1/4 teaspoons baking powder
• 1/4 teaspoon baking soda
• 1/2 teaspoon table salt
• 8 tablespoons unsalted butter , softened
• 1/2 cup vegetable oil
• 2 1/4 cups (9 ounces/255 grams) confectioners' sugar
• 1/2 cup (1½ ounces/43 grams) unsweetened cocoa powder
• 1/4 cup hot water
• 1/4 teaspoon table salt
• 2 ounces (57 grams) bittersweet chocolate , melted