Combine the oats and the milk in a mixing bowl, cover and let stand about 30 minutes. Add bran flakes and raisins, let stand 10 more minutes.
Preheat oven to 190°C.
Add cinnamon, sweetener, walnuts or pistachios. Arrange the sliced apples into a lightly greased baking pan, pour the apple juice over the apples and cover with the prepared mixture. Bake about 15 - 20 minutes.