For the curry, heat a large deep lidded frying pan or wok until hot, then add the vegetable oil and the shallots. Stir fry for one minute, then add the curry paste and stir fry for a further minute.
Add the coconut milk and bring to the boil.
Add the fish sauce, chicken thighs, potatoes and aubergines and return to a simmer. Cover with a lid and simmer gently for 15-20 minutes, or until the chicken is completely cooked through and the potatoes are tender. Add the lime juice, season, to taste, with salt and freshly ground black pepper and stir.
Meanwhile, for the rice, place the rice and lemongrass into a small saucepan and cover with the cold water. Cover with a lid and bring to the boil. Reduce the heat and simmer for 12-15 minutes, or until the rice is tender and all the water has been absorbed. Remove the lemongrass.
To serve, place the rice onto serving plates, top with the curry and sprinkle over the coriander.