Vegetarian bun rieu

Step 1: Hold 1 onion cut-side down in a dry frying pan over a high heat for about 5 minutes until the face is charred black in patches.

Step 2: Put 8 ¼ cups water, the charred onion and 10 ½ oz daikon (white radish) in a large pot. Squeeze 8 dried shiitake mushrooms, chop them finely and set them aside for the curds; pour their soaking liquid (not the grit at the bottom) into the pot. Bring to the boil, then simmer gently over a low heat for 25 minutes. The stock should smell sweet from the radish.

Step 3: Meanwhile, warm 3 tbsp vegetable oil and 1 tsp annatto seeds in a small pan over a low heat for 2 to 3 minutes, until the oil turns deep orange. Don't let it smoke. Strain out and discard the seeds.

Step 4: Crumble 10 ½ oz firm tofu into a bowl with your fingers until it looks like coarse breadcrumbs. Beat in 3 eggs, ½ tsp black pepper, half the chopped shiitake and a pinch of the ⅓ tsp salt. The mixture should be loose, like scrambled eggs before they hit the pan.

Step 5: Heat the annatto oil in a frying pan over a medium heat. Fry 3 shallots for 2 minutes until soft and golden, then add 5 ripe tomatoes and the remaining chopped shiitake. Fry for 8 to 10 minutes, pressing the tomatoes with a spoon, until they collapse into a thick, glossy red paste.

Step 6: Lift the onion and daikon out of the stock. Scrape the tomato paste into the pot and stir in 2 cubes fermented tofu (chao), 3 tbsp light soy sauce, 1 tsp sugar and the rest of 1 tsp salt. Bring back to a gentle simmer.

Step 7: Spoon the tofu-egg mixture in large dollops around the surface of the barely simmering broth. Don't stir. Within 3 to 4 minutes the curds float up, turn pale yellow and firm into soft, spongy rafts. Common mistake: boiling hard or stirring now breaks the curds into a cloudy mess, so keep the heat low and leave them alone.

Step 8: Slide in 5 ½ oz fried tofu puffs and simmer for 3 minutes so they soak up the broth. Taste and add 1 tbsp rice vinegar a little at a time until the broth is clearly sour, then adjust with salt or sugar. It should taste tangy first, then savoury.

Step 9: Cook 14 oz rice vermicelli (bún) in boiling water for 3 to 5 minutes (follow the packet) until soft and white all through. Drain, rinse under cold water and drain again so the noodles don't clump.

Step 10: Divide the noodles between deep bowls. Ladle over the hot broth, scooping curds and tofu puffs onto each. Top with 2 spring onions and serve with 5 ½ oz water spinach stems or shredded lettuce, 3 ½ oz bean sprouts, 1 handful perilla or Thai basil leaves, 1 lime and 2 red chilli on a plate so everyone adds their own.