Preheat the oven to 150°C (300°F). Fill your hot water jug and put on to boil.
In a saucepan bring the cream and milk to scalding (just prior to a simmer). Remove from heat and whisk in the cocoa powder. Add the chopped chocolate and whisk the mixture until smooth.
In a separate bowl whisk the yolks until smooth. While whisking, add about a half cup of the cream/chocolate mixture in a steady fine stream into the yolks and mix well – this will temper the eggs so they don’t curdle. Continue whisking and slowly add the remaining cream/chocolate mixture. Add the brown sugar, vanilla extract and coffee liqueur (or espresso) and whisk until well combined, but don’t over-whisk or you may create too much foam. If there is too much foam, simply let the mixture sit for 15-30 minutes until it settles.
Place ramekins in an oven proof dish (you can place a tea-towel underneath the ramekins to stop them from slipping about in the dish). Fill the ramekins with the crème brulee mixture (you can either ladle it in, or pour the mixture into a jug so that pouring is easier). Carefully pour boiled water into the oven proof dish so that it comes half way up the sides of the ramekins.
Carefully place the roasting tin with ramekins into the oven and bake until, when lightly shaken, they jiggle in the middle (depending on the oven and the size of the ramekins, this will take about 30-40 minutes). Remove the roasting pan from the oven, carefully remove the ramekins and place them on a wire rack to cool.
Once completely cooled, put the custards into the fridge (you can lightly place a piece of silver foil or plastic wrap over top, but it’s not necessary) and chill for at least four hours (but preferably overnight).
When ready to serve, sprinkle each custard evenly with 1-2 teaspoons of granulated white sugar (the more the sugar, the thicker the crust) and spread it evenly with the back of a teaspoon. Before the next step: Put each ramekin on a piece of silver foil or tray to avoid burning the bench! Using a blow torch, and one ramekin at a time, work from the outside to the inside using small circular motions (one or two inches from the surface). Let it rest for a minute, then come back for a second or third grilling. Don’t be shy about letting the sugar burn in places – it’s meant to! Let the caramelized sugar cool and harden to form a crisp layer (at least 5-10 minutes) then serve immediately.