Line a 9-inch square pan with aluminum foil. Spray foil with nonstick spray.
Bring sugar, butter and milk to a rolling boil in a large saucepan on medium heat, stirring constantly. Boil for 4 minutes, or until 234 degrees F on candy thermometer, stirring constantly.
Remove from heat. Add chocolate and marshmallow creme; stir until melted. Stir in vanilla.
Pour into pan and cool completely.
Recipe by Dallas Duo Bakes at http://dallasduobakes.com/2011/12/fantasy-fudge.html