Place the chicken stock (or broth) in a stockpot, add lemon grass, ginger and lime leaves. I recommend slicing the lime leaves along the veins almost to the midrib to allow for more flavor release. These kaffir lime leaves are used in the same fashion we season soups with bay leaves. Bring the broth to a slow boil over medium heat.
Add sliced chicken, mushrooms, water chestnuts, salt, lime juice, fish sauce and sugar, reserving more lime juice and fish sauce to add later to taste.
Cook slowly, uncovered for 10 - 15 minutes, then add coconut milk, cilantro, green onion, tomato, fresh coconut meat, bruised chilies, and red curry paste. Stirring frequently, bring almost to a boil, then remove from heat and serve if you are happy with the flavor of lime juice to fish sauce in conjunction with the other ingredients. Cook this soup gently to prevent the coconut milk from separating.