Depending on your cake mix instructions, replace 1/2 of the oil called for with melted butter (example if it calls for 1/2 cup oil: use 1/4 cup melted butter and 1/4 cup oil)
Replace the water called for in the box directions with milk
Prepare the rest according to package directions, using a mini muffin pan for the batter.
Bake as directed.
While cooking, combine the powdered sugar and milk and the tablespoon of melted butter in a bowl.
You may need to add more or less sugar or milk to get the consistency of melted ice cream.
Dip[each muffin top in the glaze, and allow to harden.