Boil the milk in a saucepan, add the rice and cook for about 35-40 minutes. In the meantime, whip the fresh or vegetarian cream with an electric whisk in a cold bowl (you could put the bowl into the fridge to cool first to maintain the temperature of the cream). Roughly chop the dark chocolate on a chopping board, pour into the cream and stir delicately, add the mint syrup and the cooked rice. Stir everything together, pour into a mould and leave in the freezer for at least 3-4 hours.