Put the chicken in a roasting tin or large casserole. Roughly chop half the ginger and put into the cavity of the chicken with the lemongrass and half the lime, then tie the legs together with string. Mix 1 tsp of the curry paste with the oil, rub it all over the chicken, then season with salt and pepper. Heat the oven to 200C/fan 180C/gas 6, cover the chicken loosely with foil, then put it in to roast. After 35 mins, take the foil off the bird. Add the potatoes to the tin, then stir them around in any juices. Roast for another 40 mins until the chicken is cooked through and golden and the potatoes are tender.

Take the chicken out of the tin and leave to rest, loosely covered. Put the tin on the hob, add the remaining curry paste, grate in the remaining ginger, then fry for 2 mins until fragrant. Stir in the coconut milk and sugar, then boil for about 5 mins until the sauce is slightly thickened.

Tip in the beans, simmer for 4 more mins (or until tender), then splash in the fish sauce, any resting juices and squeeze over the remaining lime. Scatter with the peanuts for the authentic Massaman flavour. Carve the chicken and serve with the saucy potatoes and basmati rice.