Cake: Stir flour, sugar and baking soda, then set aside.
Bring Coca-Cola, butter and cocoa powder to a boil over medium heat. Add hot
mixture to flour mixture. Stir just until combined. Add remaining ingredients, except
marshmallows. Stir until combined. Gently stir in marshmallows. They will float
to the top. Pour into a greased and floured 13 x 9-inch pan.
Bake for 30 minutes at 350 degrees F.
Transfer cake to a wire rack. Immediately spread Cocoa Topping over cake. Thoroughly
cool cake on rack.
Cocoa Topping: Bring butter, cocoa powder and Coca-Cola to boiling. Add remaining