Step 1

For the cola cake: Preheat the oven to 350 degrees F. Grease and flour a 9-by-13-inch pan.

Step 2

Sift flour and granulated sugar in a bowl. Heat butter, cocoa powder and cola to a boiling point in a small pan. Pour over flour/sugar mixture. Add buttermilk, baking soda, eggs, vanilla and marshmallows (the batter will be thin and the marshmallows will float to the top). Pour batter into prepared pan. Bake until cake is cooked, 30 to 35 minutes.

Step 3

For the chocolate cola icing: Combine butter, cocoa, cola, confectioners' sugar and vanilla in a pan and heat until it comes to a boil.

Step 4

Poke holes in the cake while it's still hot and pour the icing over the cake. Cut into squares and serve warm from the cake pan.