1. Grease a 1.4 litre (2 1/2 pint) shallow ovenproof pie dish and put the first four ingredients into it. Add a little grated nutmeg and stir gently to mix.
2. Dot the surface of the pudding with the butter.
3. Stand the dish on a baking sheet and bake at 170°C (325°F) mark 3 for about 2 1/2 hours, or until most of the milk has been absorbed and a brown skin has formed on top of the pudding.