1. Prepare the Crust:

1. Preheat oven to 325°F (160°C). In a saucepan, heat heavy cream and brown sugar over medium heat until sugar dissolves and mixture is warm (do not boil).
2. In a bowl, whisk egg yolks and vanilla. Slowly pour warm cream mixture into yolks while whisking continuously. Strain through a fine sieve to remove any lumps.
3. Divide custard among 4 ramekins. Place ramekins in a baking dish and fill dish with hot water halfway up the sides of the ramekins. Bake for 25-30 minutes, or until set but still slightly jiggly in the center.
4. Remove from oven and water bath. Let cool to room temperature, then refrigerate for at least 2 hours. Before serving, sprinkle with smoked sea salt and optionally caramelize a thin layer of granulated sugar on top with a kitchen torch.