Meanwhile, in 2-quart saucepan, mix sugar and cornstarch. In small bowl, mix cream of coconut, milk and egg yolks; gradually stir into sugar mixture. Cook over medium heat, stirring constantly, until mixture thickens and boils. Boil and stir 1 minute; remove from heat. Beat in butter and 2 tablespoons rum with wire whisk. Cool at room temperature 1 hour.