Preheat the oven to 200C/gas 6.
Put the chicken thighs in a roasting tray, trickle with the oil and season well.
Roast for 30 minutes, turning once or twice.
Meanwhile, halve and deseed the chillies, then cut each into 1cm strips.
After 30 minutes, take the chicken out of the oven and add the sliced chillies, garlic and ginger to the roasting tray.
Turn the chicken again to make sure the aromatics are evenly distributed around and under the pieces.
Roast for a further 10 minutes.
Tuck the plum halves around the chicken pieces and trickle the soy on top.
If there doesn't seem to be much liquid in the tray, add a few tablespoons of water.
Return to the oven for 10–15 minutes until the plums are soft and yielding their juices.
Baste the chicken and plums with the pan juices, then leave to rest for 10 minutes.
Finish with a scattering of chopped coriander, if you like.
Serve with noodles or plain rice.
