Add the butter, sugar, corn syrup and heavy cream to a medium-size saucepan and cook while stirring over medium heat for 5 to 7 minutes.
Once the butterscotch appears syrupy and thick, remove the saucepan from the heat and carefully stir in the bourbon. (It will sputter and boil when you do this.) Stir in a big pinch of salt and let cool slightly before serving.
Serve the butterscotch over good vanilla ice cream.