Preheat the oven to 325° F. Spray bottom only of a 9x13 inch glass baking pan with baking spray.

Have ready two large mixing bowls. In the first bowl, mix together all dry ingredients for the yellow cake batter (flour through salt). In the second bowl, mix together all dry ingredients for the chocolate batter (flour through salt).

Make the yellow batter first. Whisk the 2 eggs, yolk, vanilla and 2 tablespoons of the milk together in a small bowl. Add the butter to the dry ingredients and mash it around, then stir in the egg mixture until it’s as blended as you can get it. Add the remaining ½ cup buttermilk and beat with a handheld mixer until smooth.

Repeat the same procedure with the chocolate batter. Whisk the egg, vanilla and all the buttermilk together in a small bowl. Add the butter to the dry mixture and mash it around. Add the egg mixture and blend it as much as you can, then add the coffee and beat with a handheld mixer until smooth. Now you should have a bowl of vanilla batter and a bowl of chocolate batter. The chocolate batter will be very thin.

Pour about half of the vanilla batter into the pan. Pour chocolate batter over the vanilla, then drop spoonfuls of vanilla batter of the chocolate, allowing parts of the chocolate batter to show through.

Bake the cake for about 45 minutes or until a toothpick inserted in the center comes out clean. Let cool completely, then frost with a generous layer of Chocolate Frosting.

In a large mixing bowl, mix the butter, sour cream sugar, cocoa, salt and 2 tablespoons of the cream as well as you can, then beat with a hand-held mixer until pasty and thick. Continue adding milk until you get a nice, smooth, spreading consistency. Spread over the cake. I like to store it in the refrigerator and bring it to room temperature before serving.