Prepare the custard in the morning for the evening, or the day before for the next day. Start by preheating your oven to 200°F - 210°F (90° - 100°C).

Heat the cream and milk until just simmering. Meanwhile, whisk the egg yolks and sugar together and set aside. Pour the hot cream and milk mixture over the chopped chocolate in two additions, stirring until smooth. Then pour this chocolate mixture over the egg yolk and sugar mixture and whisk again until combined.

Pour the mixture into ramekins to a depth of about 3/4 inch (2 cm). Bake for 45 minutes to 1 hour. The custard should be set but still slightly wobbly in the center. Let cool, then refrigerate for at least 5 hours.