Beat butter and brown sugar in medium bowl with electric mixer on medium speed about 5 minutes or until light and fluffy. Beat in whipping cream and powdered sugar alternately on low speed until smooth. Stir in cloves, cinnamon, and nutmeg.
Use immediately, or spoon into a 1-quart freezer container. Cover, label and freeze up to 3 months.
For each serving, place rum and 2 tablespoons Hot Buttered Rum Batter in a mug. Stir in boiling water. Sprinkle with nutmeg.