3 pkg. of 6 oz. semi sweet chocolate chips
1/2 lb. butter
3 tsp. vanilla
4 1/2 c. sugar
1 lg. can evaporated milk

Put in large bowl chocolate chips, butter and vanilla. Put in large saucepan with thick bottom the sugar and milk. Bring to boil. Boil exactly 6 minutes form start of boil, stirring constantly.

Remove from stove and pour over ingredients in bowl and stir until batter and chips are melted and mixture begins to thicken. Pour into lightly buttered baking dish and let stand 6 hours. Cut into squares.