How to cook perfect tom yum soup

By February, even reliable comfort foods can lose their warming charm. Risotto, jacket potatoes, dal – all the old favourites which seemed so exciting back in the late autumn now seem to stretch in an unending starchy line to spring (whenever that may be). And while it’s not quite time to retire the masher for the season, a dose of fresh, dare I say “zingy” flavour in the form of a clean, aromatic soup is just the thing to shake up a hibernating palate.

Thai tom yum is just what the doctor ordered, being both hot and searingly aromatic enough to cut through even the stuffiest of winter colds. I’m informed the name simply means “mixed boil”, and that it can contain all manner of things from beef to crab, but as most recipes I found called for prawns, that’s what I’ve gone for here. As food writer Vatcharin Bhumichitr observes, however, it’s a very adaptable basic recipe which also has the benefit of being quite ridiculously quick to make once you’ve amassed the ingredients – just the thing for when you feel at death’s door.

Stock answers

The most important part of any soup, of course, is its liquid base, and with tom yum there seems to be little consensus on what form this should take. Thai expert David Thompson uses chicken stock in the recipe in his book of Thai Street Food, while Lindsey Bareham goes for fish stock in the “authentic” recipe in A Celebration of Soup. Food writer MiMi Aye takes a more simple approach, and uses just water, Allegra McEvedy goes for a combination of water and coconut milk, and Rosemary Brissenden makes a quick prawn stock for the tom yum kung in her encyclopedic South-East Asian Food.

Once the requisite aromatics have been added, I’m surprised at just how tasty MiMi’s simple soup is; I’ve substituted prawns for her mussels, which might help to explain the absence of any significant seafood flavour, but while light, the broth is nevertheless utterly delicious – and ready in under 10 minutes.

David Thompson’s recipe involves so many more ingredients, including coriander root and shallots, that to be honest, I’m hard pressed to identify any chicken flavour whatsoever in the finished soup, which is presumably the idea: it’s simply there to provide a savoury base note.

Both Lindsey Bareham and Rosemary Brissenden use the shells of the prawns to add flavour to the finished soups – the former simmers them in fish stock, while Brissenden simply uses water, which I prefer; fish stock, or the bought stuff at least, has a very distinctive flavour, which overpowers the sweet nuttiness of the crustaceans.

The coconut milk in Allegra’s vegetarian tom yum is a bit of a disappointment – the finished soup is so bland that I’m convinced I’ve left an ingredient out somewhere, but as there’s nothing left on the counter I can only suppose that its creaminess has neutralised the aromatic spice paste I’ve just made. Even with more lime juice, and a sneaky dash of fish sauce, it still lacks the arresting zing of the other versions. Vegetarian tom yum does not quite hit the spot, as far as I’m concerned.

Flavourings

Both Allegra and Rosemary Brissenden make spice pastes to add flavour to their soups. Allegra’s is a punchy mixture of garlic, lemongrass, ginger, lime leaves, coriander, chillies and shallots, which is briefly stir-fried to release the flavours before being fatally diluted with the aforementioned coconut milk and water. It gives the soup a lovely green colour, but, sadly, very little flavour indeed.

Brissenden, meanwhile, adds something called nam phrik phao, or “chilli jam”, which she claims is readily available in Asian food stores. After a cold, frustrating slog round five different such establishments in north and east London, I grudgingly decide to make my own to her recipe, although I can’t aspire to the traditional version which can only be made “when you have a charcoal barbecue or a wood fire burning”. It’s -2C outside, and there’s no way I’m ferreting out the charcoal when she also details a perfectly good “contemporary method”.

Still, that’s not a walk in the park either – peeling and finely slicing 4 tbsp garlic and 6 tbsp shallots reduces me to irritated tears. I deep fry them with 5 dried red chillies, then purée the lot with some very aromatic shrimp paste and a hefty number of dried shrimps before finishing the paste off with 2 tbsp palm sugar and 3 tbsp tamarind water – luckily, as she observes, the stuff keeps for “quite a while in the refrigerator”, because I can’t see my flatmate allowing me to make this again in a hurry. It’s surprisingly delicious – toasty, rich and sweet, but those same flavours spoil the freshness of the soup for me: I’d prefer to use this in a stir fry or to liven up some steamed rice. And, with a jar of the stuff in the fridge, I probably will.

Other ingredients

The basics of the tom yum seem to be lemongrass, lime leaves and juice and chillies – even, thanks to Allegra’s recipe, the fish sauce seems to be negotiable. After my success with MiMi’s simple but gloriously aromatic recipe, I wonder how many of the ingredients are strictly necessary – David Thompson may call for coriander roots and tamarind water, and Allegra for tomatoes and mushrooms, but for my taste, these all simply gild the lily. Shallots, although a popular ingredient, add a rich sweetness that doesn’t seem appropriate in such a clean-tasting soup, and mushrooms present a similar problem – to add bulk, I’d prefer something light like pak choi or bean sprouts.

Perfect tom yum soup

Hot, fragrant and sour is how I like my tom yum, so I’ll be sticking to the basics, with savoury fish sauce for depth and MiMi’s palm sugar for balance. The only slightly unorthodox ingredient I’ve given house room is galangal, a root which looks like ginger, but tastes far more peppery. I think it works really well with the fresh chilli, but if you can’t find it (big supermarkets often sell it dried, if you don’t have an Asian specialist handy), then I wouldn’t feel too bad about leaving it out – the soup could still blow your head off.

Serves 4

16 raw shell-on king prawns
Dash of oil
4 lime leaves, roughly torn
2 lemongrass stalks, cut into 5cm pieces and crushed
2 slices galangal (optional)
2 bird’s eyes chillies, finely sliced
1 tbsp palm sugar
Juice of 1½ limes
2 tbsp fish sauce
Handful of coriander or Thai basil leaves, torn, to serve

1. Shell the prawns and set the meat aside. Heat the oil in a pan on a medium-high flame, and fry the shells until pink. Add 1 litre of water and bring to a simmer, then strain and discard the shells.

2. Return the prawn stock to a clean pan, and add the lime leaves, lemongrass and galangal. Bring to a simmer and leave to infuse for 5 minutes, then add the chillies and simmer for another couple of minutes.

3. Add the prawns and cook through until pink, then take off the heat and stir in the sugar, lime juice and fish sauce. Taste for seasoning, and then pour into bowls. Garnish with coriander or basil and serve immediately.

Is tom yum your go-to recipe for scaring off colds, or do you have another secret weapon up your sleeve? What other spicy recipes do you favour for banishing the winter blues?