Preheat the oven to 350° Grease and line a 9x13 metal baking pan with parchment paper and set aside. **See note below on baking in two 9x13 pans if you have them!

In the bowl of a stand mixer combine the melted butter, granulated sugar, vegetable oil, vanilla extract and eggs. Mix on medium until combined.

In a medium bowl sift cocoa powder, flour, baking soda, baking powder and salt. With the mixer on low, add half of the dry ingredients, then the milk. Add the rest of the dry ingredients and the coffee. Mix until fully incorporated.

Pour into the prepared baking pan and bake for 30-35 minutes or until baked through. Remove from the oven and allow to cool for 30 minutes at room temperature before refrigerating until cold, about 1 hour or up to overnight.

In the bowl of a stand mixer beat the butter and marshmallow filling until smooth, about 1 minute. Add in the vanilla extract, powdered sugar, salt and milk. Add more milk if needed to reach desired spreading consistency. Set aside until assembly.

In the bowl of a stand mixer cream the butter, powdered sugar and cocoa powder until combined. Add in the vanilla, milk and salt and beat until smooth. Set aside until assembly.

Once the cake has completely cooled, flip the cake out of the pan. Use a serrated knife to slice the cake in half length wise, trying to make the cut as even as possible.

Place the bottom half of the sheet cake down, then add marshmallow filling, reserving about ½ cup for piping. Evenly spread and top with the other half of the cake. Refrigerate for 30 minutes or up to 1 hour.

Remove the cake from the fridge and evenly spread the fudge frosting on the top and sides of the cake.

Add extra marshmallow filling to a piping bag fit with a small round tip. Evenly space and pipe 5 small looped lines from one side to the other width wise. Slice and serve! This cake cake be stored at room temperature or refrigerated.