Notes: This sauce is excellent over ice cream. You can make it up to 3 weeks ahead; chill airtight. To heat, cook, uncovered, in a microwave-safe bowl in a microwave oven at 30% power until warm and fluid, about 2 minutes.
1. In a 2- to 3-quart pan over medium heat, tilt and swirl sugar often until melted and amber-colored, 5 to 7 minutes. Stir in cream; mixture will bubble and sugar will harden. Stir until sugar melts again and sauce boils, 6 to 8 minutes.
2. At once, pour sauce into a bowl. Stir in vanilla.
3. Let sauce cool for 10 minutes, then, if desired, stir in rum. Serve warm or cool.
Nutritional analysis per tablespoon.