Preheat the oven to 325°F (165°C).
In a medium saucepan, heat the cream and milk over medium heat until steaming. Remove from heat.
In a separate bowl, whisk together the egg yolks, sugar, vanilla, salt, and cayenne (if using) until smooth.
Slowly pour the hot cream mixture into the egg yolks, whisking constantly to temper the eggs.
Strain the custard mixture through a fine-mesh sieve into a clean bowl.
Gently fold in the crab meat until evenly distributed.
Pour the mixture into 6 (4 oz) ramekins or custard cups.
Place the ramekins in a large baking dish and fill the dish with hot water halfway up the sides of the ramekins.
Bake for 30-35 minutes, until the edges are set and the center is slightly jiggly.
Remove from the oven and let cool to room temperature.
Refrigerate for at least 4 hours or overnight until completely chilled.
When ready to serve, sprinkle a thin layer of sugar over each custard.
Use a kitchen torch to caramelize the sugar until golden brown and bubbly.
Let the sugar harden for a few minutes before serving.