"I made this using rhubarb and raspberries from the garden. You could use different fruit, and substitute toasted hazelnuts for macadamia nuts or leave out the nuts and chocolate for something more traditional. Serve with ice cream, cream, or custard. I used single cream spiked with vanilla and a tablespoon of sugar."
Combine rhubarb, raspberries, white sugar, orange juice, cornstarch, and cinnamon together in a casserole dish; cover with aluminum foil.
Bake in the preheated oven for 10 minutes.
Heat a skillet over medium-high heat; cook and stir macadamia nuts until toasted and fragrant, about 5 minutes. Combine macadamia nuts, flour, oats, butter, brown sugar, and dark chocolate in a food processor; pulse until crumbly.
Remove aluminum foil from casserole dish and stir rhubarb mixture; top with oat mixture.
Bake in the preheated oven until rhubarb is soft and top is lightly browned, about 45 minutes.