Bún Riêu Chay — When the Market Ran Short

1. 01

   Char the onions and build your broth base

   Heat a heavy pot over high heat. Char the onion halves cut-side down until blackened and fragrant, about 5 minutes — this isn't cooking, it's seduction. Tip them in with the stock and bring to a boil. Add the dried shiitake and a good crack of white pepper. Simmer for 15 minutes while you prep the rest.

   ~20 min
2. 02

   Annatto oil and tomato

   In a small pan, warm the annatto seeds in 2 tablespoons of neutral oil over medium heat until the oil turns rust-red and smells toasted, about 3 minutes. Strain through a sieve into a bowl — discard the seeds. Halve your tomatoes and add them to the broth. Stir in the annatto oil. Simmer another 10 minutes until the tomatoes collapse into the broth.

   ~13 min
3. 03

   Make the 'crab cake' tofu patties

   Crumble the firm tofu into a bowl with a fork — you want texture, not paste. Finely chop your mushrooms and fold them in. Whisk the eggs in a separate bowl, then fold into the tofu-mushroom mix. Season with a pinch of salt and white pepper. Shape into 8 small patties about the size of a golf ball, flattened slightly. Heat 3 tablespoons of oil in a separate pan over medium-high heat and fry the patties until golden and crispy on both sides, about 3 minutes per side. Set aside.

   ~12 min
4. 04

   Strain and season the broth

   Push the shiitake and tomato debris gently through a fine sieve, pressing out all their flavour into the broth. Discard the solids. Stir in the vegetarian fish sauce (or soy-salt blend). Taste. Adjust — this should taste like umami and summer tomato at once. You want it strong enough to season the noodles underneath.

   ~5 min
5. 05

   Cook the vermicelli

   Bring a separate large pot of water to a rolling boil. Add the rice vermicelli and stir immediately so it doesn't clump. Simmer for 4–5 minutes until just tender but with a whisper of bite. Drain and divide among four bowls.

   ~6 min
6. 06

   Finish and serve

   Gently place silken tofu cubes (about 75g per bowl) into each noodle nest. Ladle the hot broth over everything — it should come three-quarters up the bowl. Crumble or halve the 'crab cakes' and scatter over the top. Pile the fresh herbs and banana blossom (torn into ribbons) on a separate plate and let each diner build their own bowl. A squeeze of lime is essential.

   ~5 min

First spoon: the broth hits with savoury tomato depth and a ghost of mushroom umami, silken tofu melting on your tongue. Mid-bowl: the tofu 'crab cakes' have softened into the broth, adding a savoury earthiness. The herbs come in — sharp mint, the earthiness of perilla, coriander's green chatter. Last bite: noodles at the bottom have absorbed all that broth, sticky and flavour-packed. Finish with lime juice and you've got a soup that tastes like vegetarian conviction and summer heat in one slurp.

• ·Char the onions hard — blackened onion skin tastes better than pale timidity.
• ·Don't skip the annatto oil; it's not just colour, it's the signature that says 'riêu' to your mouth.
• ·Silken tofu must stay gentle — add it to the bowl, not the pot, so it doesn't shatter into submission.
• ·The tofu 'crab cakes' are theatre, but they work: fry them until the edges crisp, then let the broth soften them to almost-paste.
• ·Taste the broth at the end and taste it honestly — it should be salty and deep enough to flavour the noodles underneath without you adding salt at table.