1. Preheat the oven to 150° and butter a two-litre baking dish.
2. Put the butter, sugar, pudding rice, milk and cream into a saucepan and bring gently to the boil, stirring to help the sugar dissolve. Add the salt, nutmeg, lemon zest and vanilla extract and return to a simmer.
3. Simmer for about four minutes, stirring all the time, until you can feel that the rice grains have become slightly (only slightly) swollen. Pour the mixture into the prepared dish and bake for two hours. By this time the rice should be creamy and cooked, but shouldn’t be dry or overly sticky.
4. As the pudding looks beautiful baked – it develops a lovely golden skin on the top – take it to the table in the pudding dish and put the Quince Jelly and the blackberries in separate serving bowls, so people can help themselves.