Combine brown sugar and butter in a small saucepan and bring to a boil over medium heat.
Allow to boil for 2-3 minutes, whisking occasionally.
Add the cream and whisk, cooking a minute or two longer.
Whisk in vanilla and remove from heat.
Pour into container.
Use over ice cream.
Store in the fridge when not using. Microwave for 45 seconds to 1 minute to warm up.