Smoked Chicken, Wild Mushrooms, Sweet Basil, Coconut & Galangal Soup
Tom kha gai gets made badly more often than almost any other Thai soup. The usual version is sweet, creamy and mild: the coconut cream doing most of the work while the galangal sits in the background as an afterthought. It should be the opposite. Galangal forward, sharp and medicinal, with the kaffir lime and lemongrass underneath it and the chilli building slowly. The coconut cream softens all of it into something rich and complex. The line between a good tom kha and a bad one is almost always the galangal.
The chicken is cold-smoked before it goes in. At Farang we do this in the kitchen over a wood chip pan, but the easiest method at home is the same one used in the smoked salmon laksa: get a BBQ going with a little wood smoke, place the chicken breast on the cold side away from direct heat, cover and leave it for a couple of hours. The smoke flavour will sit on the chicken without cooking it, and it goes into the soup with a depth that plain poached chicken doesn't have. If you want to skip the smoking, just grill or BBQ the chicken until nicely charred, chop it up and drop it in. The soup is still very good without the cold-smoke step, just a different version of it.
The butternut squash is a Farang addition. It's not traditional to tom kha gai, but it's one of the best British autumn ingredients and it works well here. It softens into the coconut broth, takes on the galangal and lime flavour, and adds a gentle sweetness against the sharpness of the chillies. Pumpkin works equally well if that's what you have.
The nahm prik pao goes on at the table, not in the pot. It's the fried version of Thai chilli jam: chillies, shallots and garlic cooked down in oil until deep and jammy, then blended with tamarind and fish sauce. It's a different recipe from jaew, which is charred over fire rather than fried in oil. A spoonful over the bowl at the table adds concentrated heat and sweetness that changes the soup completely. Don't skip it.
Smoked Chicken, Wild Mushrooms, Sweet Basil, Coconut & Galangal Soup
Serves: 2 | Prep: 20 mins (plus 2 hours cold smoking) | Cook: 20 mins
Ingredients
1 chicken breast, skin and fat removed, sliced into rough 2cm pieces (cold-smoked as per method below, or BBQ-grilled and chopped)
¼ butternut squash (roughly 50g), peeled and cut into rough 2cm pieces (pumpkin works too)
8 Thai shallots, peeled and lightly bruised with a pestle
2 green bird's eye chillies, bruised with a pestle
2 kaffir lime leaves, torn
2 sticks lemongrass, cut into 2cm pieces and bruised with a pestle
10g galangal, peeled, cut into 2cm pieces and bruised with a pestle
2 coriander roots, cleaned and bruised with a pestle
½ teaspoon coarse sea salt
2 to 3 tablespoons fish sauce (soy sauce for a vegetarian version)
200ml chicken stock (vegetable stock for vegetarian)
300ml coconut cream
10g Thai sweet basil (regular basil works)
50g assorted wild mushrooms (enoki, shiitake and shimeji all work well)
Juice of 1 lime
2 tablespoons nahm prik pao (Thai fried chilli jam), to serve
Method
Cold smoke the chicken first. Set up a BBQ with a small amount of wood chips. Once the smoke is going, place the chicken breast on the cool side of the grill away from direct heat and cover. Leave for a minimum of 2 hours, or overnight in the fridge for a deeper smokiness. The chicken stays raw, which is fine. It will cook in the soup. Alternatively, grill or BBQ the chicken breast over direct heat until charred and cooked through, then slice into rough 2cm pieces. This gives a different result but still works well.
Blanch the squash. Bring a small pan of water to the boil, add the squash pieces and simmer for 3 to 4 minutes until just beginning to soften but not cooked through. Drain and set aside.
Build the soup base. Combine the chicken stock, 100ml of the coconut cream, fish sauce, salt, galangal, coriander roots, bruised chillies, lemongrass, kaffir lime leaves and Thai shallots in a medium saucepan. Bring to a simmer and let it bubble gently for 5 minutes. The broth should smell deeply aromatic at this point: floral from the kaffir lime, sharp from the galangal. If it still smells raw and faintly sweet, give it another couple of minutes before moving on.
Add the par-cooked squash, mushrooms and cold-smoked chicken pieces to the simmering broth. Cook gently for 4 to 5 minutes until the chicken is just cooked through and the mushrooms have softened. Don't let it boil hard or the chicken will tighten.
Stir in the remaining 200ml coconut cream and the sweet basil. Add the lime juice. Taste now: the soup should be properly salty from the fish sauce, with the lime sharp at the back and the chilli building slowly underneath. If the coconut sweetness is dominating everything else, the lime is what brings it back. If it tastes flat, it needs fish sauce before anything else. Don't adjust casually at this stage. This is where the bowl is made.
Divide between two deep bowls. Spoon nahm prik pao over the top at the table. Serve with steamed jasmine rice alongside.
Chef's notes
The aromatics in this soup (galangal, lemongrass, coriander root) are bruised rather than chopped fine because they're there to flavour the broth, not to be eaten. Leave them in the bowl while you eat and push them to the side. They've done their job by the time the soup reaches the table.
Galangal is not the same as ginger. It's harder, more fibrous and has a sharp, almost medicinal quality that ginger doesn't have. It's what makes tom kha taste like tom kha. You can find it fresh in most Asian supermarkets or frozen from a Thai online supplier. Fresh ginger is not a substitute.
Nahm prik pao is available in tins and jars in most Asian supermarkets, usually labelled as roasted chilli paste or Thai chilli jam. Maesri and Mae Pranom are reliable brands. It's worth keeping a jar in the fridge. It goes into fried rice, through noodle dishes, into salad dressings and as a garnish for soups. It's a different recipe from jaew, which is charred rather than fried, and they're not interchangeable.
Prawns work in place of the chicken in this recipe. Use the same smoked chicken stock in the base if you can, as the richness of it carries through even without the chicken itself. Add peeled raw prawns in the final 2 minutes of cooking rather than the 4 to 5 minutes needed for chicken.
A bowl of tom kha should taste of galangal first and coconut second. If it's the other way around, add more lime and more fish sauce until it isn't.
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For more recipes, signed copies of my cookbooks are available at Payst: Cook Thai and Thai in 7.
Head chef & founder of Farang London restaurant. Cookbook author of ‘Cook Thai’ & ‘Thai in 7’. Chief curry paste basher and co-founder of Payst London.