Combine all ingredients (1 cup brown sugar, 1/2 cup white corn syrup, 1/2 cup heavy cream, 1/4 cup unsalted butter, pinch of salt) except for vanilla in a medium sized saucepan over medium-low heat. Stir frequently until it comes to a boil.
Once it comes to a boil, stir and cook 5 minutes.
Remove from heat and stir in 1/2 teaspoon vanilla extract. Allow sauce to cool at least 5 minutes before using.
Pour remaining sauce into an airtight container; store up to two weeks refrigerated.
Notes
Sauce will harden when refrigerated. To reuse sauce, heat in microwave, stirring every 15 seconds until it reaches desired consistency.