Quinces and Apple Crumble with Hazelnuts

"The recipe I’m sharing here combines fragrant quinces with apples. The fruits are delicately flavored with star anise and cardamom, and topped with a crunchy layer of cinnamony hazelnuts and rolled oats. I love quinces in general and they work really well in this dessert. But as they are available only for a short period of time (at least in Germany), you might want to substitute them for other fruits such as pears, stone fruits, or berries, which will work fine too."