1. In a small saucepan over medium-low heat, melt butter.
2. Add in the cream, brown sugar and salt and mix until well blended.
3. Allow mixture to come to a boil for about 10 minutes, stirring constantly until thickened.
4. Once thickened, add vanilla and continue to whisk for about another minute.
5. Remove from heat and let cool down a bit.
6. After use, you will most likely have some left over. Store in a mason jar or any airtight container in fridge for up to 2 weeks.