Bring cream, liqueur, sugar, and vanilla to boil in heavy medium saucepan over medium-high heat, stirring frequently.
Mix cornstarch and 2 teaspoons water in small bowl to blend; whisk into cream mixture. Boil until sauce thickens, stirring constantly, about 10 minutes.
Cool, then cover and refrigerate until cold, about 2 hours
Keyword Baileys Irish Creme, beachy dessert, bread pudding, dessert topping, St. Patrick's Day