Heat the oven to 220C/425F/Gas 7.
Place the cooked rice in a medium saucepan and stir in the cream. Add the vanilla pod and seeds and heat gently for a few minutes. Add the sugar, the orange pieces and the mint. Heat for a further few minutes, stirring occasionally. Remove the vanilla pod.
Transfer to a buttered gratin dish and bake in the oven for 6-8 minutes, or until set.
Remove from the oven and serve at once.