Cook sugar and canned milk to rolling boil for 6 minutes; Stirring constantly. Use large stainless steel pot; remove from heat. Add butter, chocolate chips, vanilla, and dash of salt Stir until mixed. Pour into buttered pan. Let stand 6 hours before cutting. Will keep a long time in cookie tin or a sealed container in a cool place.
* The original recipe calls for 1/2 lb butter, but I find that the butter "pools" on top of the finished fudge. I only use 12 T of butter and my fudge turns out fine!