Toss the onion wedges in 1 tablespoon of the oil in a large roasting tin. Slash each chicken joint 2–3 times with a knife, then add to the roasting tin with the plums.
Warm the redcurrant jelly, vinegar, soy sauce and 5–spice in a small saucepan until the jelly has melted, then brush liberally over the chicken, reserving about one-third for later. Pour the measured water into the base of the tin, avoiding the chicken, so that the glaze will not burn on the bottom of the tin.
Roast, uncovered in a preheated oven, 190°C (375°F), Gas Mark 5, for 40–45 minutes, brushing with the remaining glaze once during cooking. Test the chicken (see
Heat the remaining oil in a frying pan and add the pak choi. Fry for 2–3 minutes until tender and then add to the roasting tin just before serving.
Spoon on to plates and serve with rice.