1. Heat the oil in a wok or large frying pan and add the chicken. Cook over a medium-high heat for 4-5minutes, stirring occasionally, until the chicken is sealed and browned. Add the onion, garlic and mushrooms and cook for a further 2 minutes.
2. Add the chilli, lemongrass, ginger, coconut milk, chicken stock and red curry paste. Stir in the fish or soy sauce.
3. Bring to the boil, then reduce the heat and simmer for 20-25 minutes, until the chicken is cooked through. Remove the lemongrass from the sauce.
4. Serve, garnished with basil and accompanied by boiled or steamed rice.