Peel the quinces, cut them into eighths, remove the cores, and dice them into bite-sized cubes.
Add the diced quinces, the orange juice, star anise, cardamom seeds, and rice syrup to a pot. Bring to a boil, then reduce the heat, cover with a lid, and let simmer gently for about 10 minutes.
Meanwhile, preheat the oven to 160°C (320°F), fan on.
Peel and core the apples, then cut them into cubes. Add them to the pot and simmer for another 5 minutes, until all the fruit is soft but still holds its shape.Tip: Don’t toss the apple peels; you can turn them into crispy apple peel chips.
For the crumble topping, mix the oats, chopped hazelnuts, cinnamon, sugar, and oil until crumbly.
Transfer the fruit mixture to your baking dish and sprinkle the crumble evenly on top.
Bake for about 20 minutes, until the hazelnuts are golden.