In double boiler, melt chocolate chips and condensed milk until just heated. Stir until smooth. Remove from heat and add vanilla. Stir and put in a bowl, cover with plastic wrap and cool for 2 hours.
Remove from refrigerator, and with plastic gloves, mold into ghost shape and flatten on waxed paper. Set aside in refrigerator. In small saucepan, heat marshmallows and 1 tsp. butter until smooth, set aside.
After cooled and set, spread approx 1 Tbs. marshmallow sauce over top of ghost. Immediately decorate with Halloween candies. It is also fun to make a pumpkin!