Cook a viscous porridge for pudding in the ratio of rice (preferably round grain) to milk – 1: 5 or 1: 6, respectively; over low heat, stirring constantly.
Add egg to rice porridge, mix. Add vanilla sugar.
Fill the muffin tins with rice porridge, not reaching the top. Place them in a large saucepan. Pour water so that its level reaches half the height of the molds. Cover the pot with a lid and simmer the rice puddings for 40 minutes.
Cool the steamed rice puddings and remove from the molds. Sprinkle grated chocolate over the rice puddings, if desired.