Step 1

Toast the gram flour over a low heat in a dry frying pan, stirring often, until it turns golden – keep watch of it so it doesn’t burn. Set aside, then toast the ground rice or rice flour in the same way.

Step 2

In a large pestle and mortar, pound the lemongrass, chillies,,onion, garlic and ginger to a paste (or use a mini food processor).

Step 3

Heat the oil in a large deep saucepan over a medium heat. Add the turmeric, paprika and the lemongrass/chilli paste, then fry for 5-7 minutes until the onion in the paste starts to caramelise.

Step 4

Stir in the mackerel (with the brine), then cook for 5 minutes more, ensuring all the mackerel is coated with the paste.

Step 5

Add the toasted gram and rice flours and keep stirring until the paste thickens.

Step 6

Pour in 1.5 litres water and add the fish sauce. Bring the soup up to the boil, then reduce the heat and simmer for 15 minutes.

Step 7

Add the whole shallots and a pinch of pepper to the soup, then simmer gently for 30 minutes more (see Make Ahead).

Step 8

Meanwhile, put the vermicelli in a separate large heatproof bowl and pour over boiling water from the kettle. Leave to soak for 7 minutes (or until the noodles are soft), then drain.

Step 9

To serve, divide the vermicelli noodles among 6 bowls. Ladle over the fish soup (leaving behind the whole shallots), then garnish with coriander, halved eggs, red onion, fresh lime wedges, extra fish sauce, crispy onions and chilli flakes.