Cake: Preheat oven to 350. Line bottoms of two greased 9 inch round baking pans with parchment paper, grease paper also. Divide marshmallows between pans. In a large bowl, whisk flour, sugar and baking soda. In a small saucepan, combine the butter, cola and cocoa; bring just to a boil stirring occasionally. Add to flour mixture, stirring just until moistened.