Cake: Heat oven to 350 degrees F. Grease and flour a 13 x 9-inch baking pan.
Mix together Coca-Cola, cocoa and butter. Pour Coca-Cola mixture over dry ingredients,
stirring to blend. Add buttermilk and eggs. Blend well. Add marshmallows. (This
batter is thin and marshmallows will float.) Pour in prepared pan.
Bake for 40 minutes or until done. Let cool, then frost.
Frosting: Bring butter, cocoa and Coca-Cola to boiling, then pour over sugar.
Add vanilla extract and nuts. Spread over cake while hot.