Aguachile

Cut the prawns in half lengthways, along the back, removing the black vein running through the centre. Give them a quick wash, pat dry with kitchen paper and chop into pieces. Put onto a plate, sprinkle with 1 tsp salt, and transfer to the fridge while you make the chilli water.

Bash the chillies with a pestle in a mortar until you make a vibrant green paste. Add a little coarse salt to help break the skins down if you need to (or you can whizz in a small blender). Stir in the lime juice and garlic. Scrape into a bowl and season generously. Toss in the prawns, so they are completely coated, and chill again for 30-40 minutes while you prep the other ingredients. Stir after about 10 minutes so the prawns marinate evenly.

Check the prawns, they should be pink, and opaque. Keep marinating if they still have a little greyness. Add the onion, cucumber and avocado to the prawns, toss lightly, and then tip onto a platter or plates. Scatter over the coriander, and serve with tortilla chips.