A Chocolate Cake That's Got It All — Three Many Cooks

Ingredients

• 2 cups sugar
• 1¾ cup cake flour
• 2 tablespoons cornstarch
• 1 teaspoon baking soda
• ¾ teaspoon salt
• ⅔ cup unsweetened cocoa
• 1 teaspoon instant coffee
• ¾ cup boiling water
• ½ cup sour cream
• 1 teaspoon vanilla extract
• 12 tablespoons butter, melted
• 4 egg whites, at room temperature
• 1 recipe Double Chocolate Frosting
• 4 egg yolks (leftover from cake) with enough milk added to equal ½ cup or ½ cup egg substitutes
• ½ cup unsweetened cocoa powder
• ½ teaspoon instant coffee
• ¼ teaspoon salt
• 4 ounces unsweetened chocolate, melted
• 1 stick (8 tablespoons) butter, at room temperature
• 3 cups confectioners’ sugar (sifted if it contains hard lumps)
• 4 teaspoons corn syrup