In a pan on the stove top mix together Coca Cola, butter, oil and the cocoa powder and hear over medium heat until it boils then turn off the heat.
Add the marshmallows and stir until they are completely melted.
To your stand up mixer bowl add sugar, flour and salt and mix on low. Slowly pour in hot cocoa mixture and mix on medium speed then add in eggs, buttermilk, baking soda and vanilla extract and beat until well combined.
Spray a 9x13 sheet cake pan with non-stick baking spray. Pour the cake batter into the pan and spread out evenly.
Bake for 40 to 50 minutes until a toothpick inserted into the center comes out cleans or with just a few crumbs on it.
For the Frosting
When the cake is almost done add the butter, cocoa powder, milk, Coca Cola, Vanilla extract and confectioners sugar into a pot over medium high heat and whisk together until boiling and well mixed.
When the cake is done pour the frosting over it right away and spread evenly then let cool before serving.
I honestly enjoyed this cake best on it's own but my kids absolutely loved it still slightly warm served with Vanilla ice cream!
Keyword chocolate cake, coca cola, coca cola cake, cola cake