Yotam Ottolenghi's hot and sour mushroom soup recipe

A variation on Asian soups such as Thai tom yum or Vietnamese pho. The key is the stock, which must be rich and hearty, with many layers of flavour. That's why the ingredient list is so long, though I have a hunch you'll find it worthwhile. This soup is intentionally light, but can be bulked up with the addition of cooked rice noodle. Serves four. 3 medium onions, peeled and cut into large pieces 3 medium carrots, peeled and cut into large pieces 6 sticks celery, roughly chopped 6 garlic cloves, peeled 75g ginger, peeled and roughly chopped Vegetable oil 3 lemongrass stalks, very roughly chopped 12 prunes 3 red chillies, roughly chopped 6 star anise 2 tbsp soy sauce 6 lime leaves 30g chopped coriander root 120g enoki mushrooms 120g white mushrooms, sliced 160g shimeji mushrooms Juice of 2 limes 20g coriander leaves, plus extra 20g Thai basil leaves 160g bean sprouts 160g green beans, blanched for four minutes and refreshed 4 tsp tamarind paste ½ tsp salt Toasted sesame oil, to finish In a large pan, char the onion, carrot, celery, garlic and ginger in a tiny amount of oil. Cook for five minutes, or until the edges begin to colour. Add 2.25 litres of water, the lemongrass, prunes, chillies, star anise, soy, lime leaves and coriander root. Cook on a low simmer for at least 45 minutes, to infuse. Strain the stock, return to the pan (you can discard the vegetables, but I love the carrot and celery) and bring to a very low simmer. Add the enoki and white mushrooms and cook for a minute. Add the remaining ingredients apart from the sesame oil, and heat through for a minute. Taste, adjust the seasoning as needed, and ladle into warm bowls. Finish with sesame oil, not more than a few drops in each bowl, and coriander leaves. • Yotam Ottolenghi is chef/patron of Ottolenghi in London.