Mix cake mix and bake as directed ... heat and add marshmallows. Stir until melted. Stir ... add butter and chocolate chips. Stir until melted. Mix ... baked the day before.
Bake at 350 degrees approximately 30 minutes. Put marshmallows on top of cake while hot, thin icing, pour ... marshmallows while hot. Delicious! Yum yum!