Preheat oven to 220ºC, fan 200ºC, gas mark 7.
Toss the butternut squash wedges with the sweet rice wine and olive oil until evenly coated, thn spread out on a roasting tray.
Roast for 20 minutes, turning once halfway through, until golden and tender.
Meanwhile, for the caramelized plums, place the sugar in a saucepan over a high heat and cook for 1-2 minutes until light caramel starts to form.
Add the red wine vinegar (be careful as it will sizzle) and cook gently to dissolve the caramel. Add the plums and cook for 1-2 minutes until the plums soften, then set aside to cool.
Heat the vegetable oil in a wok and stir fry the duck for 2-3 minutes, until cooked to your liking.
Arrange the watercress, butternut squash and duck on plates, spoon over the caramelized plums, add the walnuts and drizzle with walnut oil to serve.