Preheat oven to 325°F (163°C). Place six 6-ounce ramekins in a deep baking dish or roasting pan. Bring a kettle of water to a boil and set aside.

In a medium saucepan over medium heat, combine the coconut milk and heavy cream. Heat until small bubbles form around the edges and the mixture is steaming but not boiling, about 5 minutes. Remove from heat.

In a large mixing bowl, whisk together the egg yolks, 1/2 cup granulated sugar, vanilla extract, coconut extract, and salt until smooth and pale yellow, about 1 minute.

Slowly pour the hot coconut cream mixture into the egg yolks in a thin stream while whisking constantly to temper the eggs. This prevents them from scrambling.

Pour the custard mixture through a fine-mesh sieve into a large measuring cup or pitcher with a spout for easy pouring. Discard any solids caught in the strainer.

Divide the custard evenly among the six ramekins. Carefully pour the boiling water into the baking dish until it reaches halfway up the sides of the ramekins.

Bake for 35 to 40 minutes, until the custards are set around the edges but still jiggle slightly in the center when gently shaken. The surface should not look wet or liquidy.

Carefully remove the ramekins from the water bath using tongs or a towel. Let cool to room temperature for 30 minutes, then refrigerate uncovered until completely chilled and firm, at least 4 hours or overnight.

Just before serving, pat the surface of each custard dry with a paper towel. Sprinkle 1 tablespoon of superfine sugar evenly over each custard in a thin layer.

Position the oven rack 4 inches from the broiler element and preheat the broiler on high. Place the ramekins on a baking sheet and broil for 1 to 3 minutes, rotating the pan as needed, until the sugar melts and caramelizes to a deep amber color. Watch constantly to prevent burning. Let the sugar harden for 2 minutes before serving.