Pour the remaining 10 cups water into a large pot, and bring to a boil. Place chicken in the pot. Stir in kaffir lime leaves, lemon grass, green onions, garlic, tomatoes, fish sauce, mushrooms, cilantro, red chile peppers, and tamarind soup base. Cook chicken 30 minutes, or until juices run clear. Remove chicken from pot, debone, and chop. Return meat to the soup, and discard bones. Serve over cooked rice.