Good-Cooking - Red Velvet Ice Cream Cake

Ingredients

• 1/2 cup (1 stick) butter or margarine, softened
• 1 1/2 cups granulated sugar
• 1 teaspoon vanilla extract
• 2 large eggs
• 1 (1 ounce) bottle red food coloring
• 2 cups all-purpose flour
• 1/4 cup unsweetened cocoa powder
• 1 teaspoon salt
• 1 cup buttermilk or sour milk (see note)
• 1 1/2 teaspoons baking soda
• 1 tablespoon white vinegar
• 1/2 gallon vanilla ice cream
• 1/2 cup solid vegetable shortening
• 1/2 cup butter or margarine
• 1 teaspoon vanilla extract (clear, if available)
• 4 cups sifted confectioners' sugar (approximately a 1-pound box); sift before measuring
• 2 tablespoons milk