Preheat the oven to 180°C.
Whisk the egg yolks and muscovdo sugar in a bowl till light and frothy, about 2 mins.
Gently heat the coconut milk and cream in a saucepan until quite hot but not boiling. Add the salt and the vanilla. Switch off the heat.
Chop the chocolate bar, place in a glass bowl and pour the hot cream mixture over to melt the pieces. Stir the chocolate into a smooth, lump-free mixture.
Whisk a tablespoon of the chocolate cream into the egg. Follow by whisking in a few more tablespoons of cream into the egg (this helps temper the eggs and prevents them from being scrambled by the hot cream). Finally whisk all the cream into the eggs.
Pour the custard into 150-ounce ramekins and place in a baking tray. Put the tray in the preheated oven and pour boiling water to the tray to reach halfway up the height of the ramekins.
Cook the custards for 20-25 minutes, till they're set but still have a slight wiggle in the centre. Remove from the oven, bring to room temperature and chill in the refrigerator for 3-4 hours or overnight.
Before serving, gently blot the surface of the custards using kitchen paper. Sprinkle 1 tbsp demerara sugar over each custard and brulee or burn the sugar with a blowtorch. This will give it a crust of caramelised sugar.
If you don't have a blowtorch, heat the head of a spoon over a flame (while holding the other end with thick oven mittens so you don't burn your hand) till it's red hot. Then gently press the sugar on the surface of the custard with the back of the spoon till the sugar caramelises. Do this for a few times for each custard till all of them have a crackly crust