Preheat oven to Gas 6, 200°C, fan180°C. Place all the ingredients for the spiced plums and star anise sauce together in a pan, partly cover and simmer very gently for 20 minutes.
Switch off heat, remove lemon zest, add some black pepper and put to one side.
Season the duck breasts and then place skin side down in a hot ovenproof frying pan with a tiny bit of oil. Fry for 5 minutes, then pour out the excess fat. Fry for another 5 minutes, then roast in the oven for 10 minutes. Switch the oven off, turn the duck skin side up and leave to rest.
For the risotto, heat the olive oil and butter in a large pan and, when the butter is foaming, add the onion and garlic and cook on a very low heat for about 5 minutes to soften. Heat the stock in a separate pan and keep it simmering away.
Add the rice to the onions and garlic, turn up the heat and stir constantly. Pour in the wine straight away. Keep stirring until evaporated. Over a low heat, add the stock a ladleful at a time, stirring and allowing each amount to absorb fully before adding another. This should take about 25 minutes. The rice should be plump and fluffy but still have a little bite at the centre of each grain. Take the risotto off the heat and allow to rest briefly, covered with a lid. Add parsley.
Slice the duck very thinly and serve on top of the risotto, adding the sauce just at the final moment.
Instead of plums you could use dark cherries or, for a savoury version, try diced aubergine and star anise.