Dad's Christmas Fudge

Every Christmas, Dad makes this fudge by the ton.

1 1/2 c. sugar
1/2 c. butter
2/3 c. evaporated milk
7 oz. jar of Jet Puff marshmallow cream
3 c. semi-sweet chocolate chips
1 c. walnuts, chopped
1 1/2 tsp. vanilla

Melt butter over medium heat. Add sugar, evaporated milk, and marshmallow cream. Bring to a boil over medium high heat stirring constantly. Cook, stirring, for 5 minutes. Turn off heat and add chocolate chips and vanilla. Stir until melted then add nuts. Pour into a buttered 9x9 or 11x7 pan. Refrigerate overnight until set. Take out an hour before cutting.