To start making your frosting- Place saucepan on burner on low heat and combine the 32 marshmallows and 2/3 cup of milk. Allow to heat until marshmallows dissolve then remove from heat. Mix, then allow it to set away from heat until it reaches room-temperature.
Using a hand mixer on a medium speed setting, mix the butter (AKA creaming) until the consistency becomes light and airy
Continue beating, slowly adding the milk and marshmallow mixture to the butter, then add the vanilla. Keep beating until the marshmallow icing becomes a stiff consistency.
Try using different coloured marshmallows or food colouring.