Heat the oven to 140C/fan 120C/gas 1. Bring the milk and cream to the boil and pour over the pieces of milk and dark chocolate and stir until melted. Once smooth, stir the beaten eggs and yolk to the mix and pour into the prepared tart case. (It’s easier to do this on the oven shelf, if you can, to avoid moving it when full.) Try to ensure there are few bubbles in the mix. Cook for 40-50 minutes, or until just wobbly.The custard should move slightly, as a whole piece, if it’s a little under, keep cooking and check it at at five-minute intervals until the right wobble is achieved.