Beat first 5 ingredients in a large bowl at medium speed with an electric mixer until light and fluffy. Stir in ice cream; freeze in an airtight container until firm.
Combine ice-cream mixture, bourbon, and coffee in a large bowl, stirring well. Or for 1 serving, combine 3 tablespoons ice-cream mixture, 3 tablespoons bourbon, and 3/4 cup coffee in a large mug, stirring well. Serve with sweetened whipped cream; garnish, if desired.
Note: Ice-cream mixture may be frozen up to 1 month.