Heat a heavy-bottomed saucepan over medium flame/heat. Then add butter. Here I have used salted butter but you can also use unsalted one, just add a pinch of salt to it.
After the butter melts, add cream and brown sugar to the pan. Don’t stir it, just give it a good swirl.
Bring it to a boil and then reduce the flame/heat to low. Keep cooking it, undisturbed, for 5 minutes or until it thickens a little (The sauce thickens significantly as it cools, so don’t cook it for too long).
Turn the heat off and pour vanilla essence. Mix well. Pour it into an airtight jar/container. Once it cools down, place it in the refrigerator and you can use it for up to 6-8 weeks.