Melt chocolate with water in microwave safe bowl on medium power for about 3 minutes; remove from oven and stir to melt completely. Add sugar. Microwave on medium power for approximately 4 minutes or until sauce comes to a boil and boils 2 minutes, stirring twice.

Add liqueur and butter; mix well. Makes about 2/3 cup sauce. Store in refrigerator. To reheat sauce, microwave on medium power.