Step 1

Preheat oven to 350º. Butter a 9 x 13 baking pan.

Step 2

In the bowl of a stand mixer, whisk the flour and sugar together.

Step 3

In a medium saucepan, add butter, Coca-Cola, cocoa, and buttermilk and bring it to a boil over medium heat. Pour it over the flour mixture.

Step 4

Add baking soda, eggs, vanilla,  and mix on low speed until well combined. Add marshmallows and mix until combined. Pour into the prepared baking dish and smooth the top with an offset spatula. Make sure the marshmallows are evenly disbursed and not all in the center.

Step 5

Bake for 40-45 minutes until a toothpick comes out clean in the center. (If you go through a marshmallow it will be sticky, so try to find a spot without a marshmallow. The center should be set)

Step 6

With 10 minutes left of the cooking time, make the frosting. It should be warm when added to the cake.

Step 7

In a saucepan, heat the butter, Coca Cola, and cocoa over medium heat until it comes to a boil. Remove from the heat and whisk in powdered sugar and vanilla until smooth. Then add the chopped pecans.

Step 8

Once the cake is done, pour the warm frosting over the warm cake. If the frosting has cooled and is too thick, add a tablespoon of Coca Cola and gently heat it so that it can be spread over the top. It will thicken as it cools.

Step 9

Let it cool completely before cutting.