Bring the milk to the boil in a wide saucepan. Cut the vanilla pod in half lengthwise and scrape out the pulp with the back of a kitchen knife. Add pulp, pod and sugar to the milk, simmer for about 2 minutes. Remove the pod.
Stir in rice pudding, bring to the boil again while stirring and allow to swell over a low heat for approx. 25 minutes. Remove from the stove.
In the meantime, preheat the oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer). Finely chop the chocolate and stir into the rice pudding. Peel bananas and cut them into approx. 3 mm thin pieces.
Grease four small ramekins or a large form (approx. 1 l capacity) with butter, works well with a piece of kitchen paper. Put banana pieces into the casserole dish or mould and spread rice pudding on top.
Sprinkle each with 1 teaspoon of cinnamon. Bake rice pudding in a hot oven for about 30 minutes until a golden skin forms. Serve hot or cold.