Fanny Farmer Fudge

Fanny Farmer Fudge 4-1/2 cups sugar 1 13-oz. can evaporated milk 2 sticks butter 12-oz. pkg. chocolate chips 6-oz. pkg. chocolate chips 1 square unsweetened chocolate, chopped 1 tsp. vanilla Combine sugar and milk in heavy saucepan and bring to a rolling boil. Stir constantly during this time, as the milk can burn easily. Boil 10 minutes, stirring constantly. Place remaining ingredients except vanilla in a large bowl. Pour the sugar/milk mixture over and beat and blend until everything is melted and smooth. Add vanilla and beat. Pour into 9x13" buttered pan and let cool.