In a large pot, combine whole milk, half and half, and heavy cream. Cook on high for 2-3 minutes or until the milk is warm but not at a boil. Reduce to medium heat, whisk in cocoa powder and granulated sugar.
Stir in the semi-sweet chocolate chips. Continue to stir until the chocolate is completely melted. Carefully pour into four mugs. Top with mini marshmallows and whipped cream.
Want to really warm up? Add 2oz. Kahlua to each mug!