1. Combine the butter, sugars and cream in a small, heavy-bottomed saucepan. Stir this mixture over low heat until the sugar dissolves, then increase the heat to medium and bring the sauce to a very gentle boil, stirring all the while.
Cook 5 more minutes, then remove from the heat and stir in the brandy or other liqueur. Serve immediately, or cool to room temperature, then cover and refrigerate until needed, up to 3 days. To rewarm, either microwave the uncovered sauce on low power or transfer the cold caramel to a saucepan and stir over low heat until warm.