In a medium saucepan, combine the brown sugar, salted butter, heavy cream, and light corn syrup.
Place over medium-low heat. Stir gently until the butter melts completely and the sugar dissolves, about 8-9 minutes.
Once fully melted and smooth, continue cooking for 3-4 more minutes, stirring frequently, until the mixture thickens slightly.
Remove the saucepan from the heat. Stir in the vanilla extract and kosher salt until fully incorporated.
Let the butterscotch sauce cool in the pan for a few minutes; it will continue to thicken as it cools.
Pour into a heatproof jar or container. Cool to room temperature before covering.
Store in the refrigerator for up to 2 weeks. Reheat gently (microwave in short bursts or over low heat) and stir before serving.
Drizzle this golden goodness over ice cream, pancakes, waffles, brownies, or use as a dip for fresh apple slices. It makes everything taste like a cozy treat!