Combine milk, chips and sugar in a saucepan and place over medium heat, whisking constantly until chocolate is melted. Bring mixture to a boil and cook 1 minute. Remove from heat and whisk in the butter and bourbon. Pour into jars and cover tightly. Store in the refrigerator.
Hot fudge sauce will keep in the refrigerator for up to 4 weeks.
This can be made in the microwave oven. Combine the milk chips and sugar in a microwave-safe bowl and heat at 100% at 1 minute intervals until the mixture boils, about 3 minutes total cook time. Whisk well between heating. Stir in butter and bourbon and whisk to incorporate. Pour into jars.Sometimes evaporated milk is confused for sweetened condensed milk. Be sure to get the right canned milk!