Put chocolate chips, butter and heavy cream in a microwave safe bowl. Cook for 20 seconds and mix. If not completely melted, do another 10 seconds and mix again. Repeat, until everything is melted.
Dip the marshmallows into melted chocolate, and immediately sprinkle with Christmas sprinkles.
Line the baking sheet with parchment paper. Arrange marshmallows on the baking sheet, and put in the refrigerator for 30 minutes for chocolate to set.