Gâteau Glaçage au Caramel à l’Ancienne

In a small saucepan, combine the brown sugar, heavy cream, and butter.
Bring to a boil over medium heat, stirring constantly.
Reduce the heat and let simmer for 2-3 minutes until thickened.
Remove from heat and stir in vanilla extract.
Pour the warm caramel glaze over the cooled cake, allowing it to drip down the sides for a rustic look.