This soup brings back so many memories of lunches with colleagues back in Hamburg, Germany, of all places. We had an excellent Thai restaurant across the road and whenever we had a business lunch, we'd go there. Their Tom Kha Gai soup was amazing, and after all these years I have finally recreated it at home!
The coconutty both is so bursting with flavour I always find it hard to not eat the whole pot by myself. Spiked with Thai essentials like galangal, lime juice, fish sauce, lemongrass and Kaffir lime leaves, this is sure to be a winner. It's super easy to make, the hardest part is probably peeling the galangal!
about 1 cup water (depending on the consistency of the coconut milk)
Wash the coriander well in a bowl full of water, swishing the greens and roots around until completely free of dirt. Cut the upper portion, the leaves, of the stems off and set aside for garnish. Keep the roots (we use these for the soup base). Cut the lemongrass off where the white base portion ends and discard the tops. Pound the lemongrass until they crack open (I used a meat tenderiser, but a rolling pin would do the same job). Slice the shallots. Peel and cut the galangal into chunks and pound with the meat tenderiser. Tear the lime leaves into smaller pieces. Slice the mushrooms. Peel and press down on the garlic with the flat side of a knife. Chop the chilli roughly into a few pieces.
In a medium saucepan, place the coconut milk, coriander roots, lemongrass, shallots, chilli, galangal, lime leaves and garlic. Bring to a mild simmer and with a lid on, cook for about 15 minutes.
Meanwhile, cut chicken into small pieces. Strain the soup through a sieve into bowl. Discard all solids. Give the pot a quick rinse and dry. Then add the coconut and gently cook the chicken. Pour the soup back into the pot. Add the sliced mushrooms, lime juice, fish sauce and water until it is the right consistency. Bring soup up to a light simmer to cook the mushrooms slightly. Do not boil. Season to taste and serve immediately with coriander and thinly sliced lime leaves.