Preheat your oven to 300°F (150°C). Start heating a kettle or pot of water for the water bath.

Pour the heavy cream into a small saucepan and heat it over medium-low heat just until tiny bubbles appear around the edges. Do not boil. Turn off the heat and set aside.

In a medium mixing bowl, whisk together 4 egg yolks, a pinch of salt and pepper, lemon zest, and Old Bay seasoning until smooth and slightly paler in color (about 1 minute).

Slowly stream the warm cream into the egg mixture while whisking constantly to temper the eggs. Optionally, strain the mixture through a fine mesh sieve into a clean bowl for a silky texture.

Stir in the lump crab meat (well-drained and shell-free), chopped chives, and grated parmesan if using. Gently fold until well combined.

Place ramekins on a deep baking dish or roasting pan. Pour the mixture evenly into the ramekins, leaving about ½ inch at the top.

Carefully pour hot water into the baking dish around the ramekins, about halfway up the sides, to create a water bath.

Bake for 30 to 35 minutes, or until the edges are set and the center has a slight jiggle. Remove from oven and lift ramekins from the water. Cool on a wire rack for about 30 minutes.

Transfer ramekins to the fridge and chill for at least 2 hours (or overnight) until firm and custardy.

Right before serving, sprinkle a thin, even layer of raw sugar or grated parmesan over each ramekin. Use a kitchen torch to caramelize the top until golden and crisp, or place under a hot broiler for 1–2 minutes, watching closely.