Spicy and sour Isan pork rib soup (Tom saep)

1. Cut the pork ribs into single ribs, blanch in boiling water for 5 minutes, drain and rinse.

2. Cover with fresh water, salt, and add the bruised lemongrass, sliced galangal, torn lime leaves and crushed shallots; simmer covered over low heat for 1.5 hours until the meat is tender.

3. Meanwhile toast the sticky rice in a dry frying pan, shaking constantly, until golden brown, then grind to a coarse powder in a mortar.

4. Take the soup off the heat and season with the fish sauce, lime juice and chilli flakes – it should be boldly sour and hot.

5. Stir in the toasted rice powder, mint and coriander.

6. Serve hot with sticky rice.

Tip: A fiery soup from Isan in north-eastern Thailand; toasted rice powder gives its distinctive nutty aroma and thickens it slightly. Make the rice powder in a bigger batch – it keeps for weeks in an airtight jar and you'll need it for larb too.