Remove the hard outer leaves and roots from the lemongrass. Crush the stalk and cut into pieces. Wash the lime leaves, chop them coarsely if necessary. Wash galangal, cut into slices. Boil up everything with 3/4 l water and broth. Wash the fillet and simmer covered for 15-20 minutes.
Clean the mushrooms, rub and possibly cut them into smaller pieces. Wash and chop the tomatoes. Carve, seed, wash and finely chop the chilli
Take out the meat. Add the mushrooms, tomatoes, chilli and coconut milk to the broth and simmer for another 10 minutes. Cut meat into strips, heat in the soup. Season soup with soy sauce and juice. Wash the chives, chop finely, sprinkle on top