Rub the chicken skin with the seven-spice seasoning. Heat the oil in a flameproof casserole and fry the chicken on all sides until lightly browned. Scatter in the garlic, chilli and ginger and fry for 1 minute.
Add the stock and bring to the boil. Cover and place in a preheated oven, 180°C (350°F), Gas Mark 4, for 45 minutes.
Put the lemon grass, fish sauce, sugar and lime juice in a food processor. Roughly chop the coriander and spring onions and add to the processor with the turmeric. Blend until finely chopped. Add the coconut milk and blend until smooth.
Pour the spicy milk over the chicken and return to the oven for a further 45 minutes until the chicken is very tender.
Remove from the oven and stir the spinach and rice noodles into the sauce around the chicken. Leave to rest for 10 minutes, then serve.