Photograph: Martin Poole
Preheat the oven to 200°C, fan 180°C, gas 6. In a bowl, mix the chilli, ginger and garlic. Finely chop half the coriander and add to the chilli mixture. Loosen the chicken skin from the breast meat with your fingers and carefully spread as much of the chilli mixture as you can under the skin, reserving a little for scattering over the top. Put the remaining coriander into the cavity of the chicken, reserving some sprigs to garnish and put the chicken in a casserole dish. Drizzle the chicken with oil; season and scatter over the reserved chilli mixture. Add the hot chicken stock to the casserole and pot roast the chicken for 1 hour, uncovered, or until cooked through.
Put the chicken on a carving board (if you added baby new potatoes to the pot, as suggested above, remove them), tipping any juices from the cavity back into the casserole dish. Cover the chicken with foil and leave to rest.
Put the dish over a medium heat and pour in the coconut milk. Whisk into the juices and simmer for about 5 minutes until reduced slightly. Check the seasoning. Carve the chicken and serve with the coconut sauce drizzled over and garnished with the reserved coriander sprigs.
Kitchen secret: pot roast baby new potatoes with the chicken and stir-fry wedges of pak choi, to serve.