Preheat the oven to 320°F (160°C).
In a saucepan over medium heat, warm the heavy cream until steaming but not boiling. Stir in salt, black pepper, and nutmeg.
In a mixing bowl, whisk egg yolks. Slowly pour in the warm cream mixture while whisking continuously to prevent curdling.
Strain the custard through a fine-mesh sieve to remove any lumps. Stir in lemon zest, if using.
Divide the crab meat evenly among four ramekins. Sprinkle chopped herbs over the crab.
Pour the custard mixture over the crab, filling the ramekins almost to the top.
Place the ramekins in a baking dish and pour hot water into the dish until it reaches about one-third of the way up the sides of the ramekins.
Bake for 35-40 minutes, until the custard is set but slightly jiggly in the center.
Remove from the oven and let cool to room temperature. Cover and refrigerate for at least 3 hours or overnight.
Before serving, sprinkle a thin layer of granulated sugar over each custard. Use a kitchen torch to caramelize the sugar until golden and crispy.