Pound the chopped chilli in a pestle and mortar with the onion and salt. When they’re broken down to a lumpy paste, add the avocado and break up the flesh roughly with a fork (keep it a bit lumpy).  Depending on the size of your pestle and mortar, it might be better to transfer the chilli and onion mixture to a bowl and then add the avocado to the bowl.

Stir in the lime juice, to taste (I try half first, then add the other half if I think it’s needed – which I usually do for a large avocado), and the chopped coriander. Serve immediately.   It will keep overnight in the fridge in an airtight container.