Start by making your guacamole. Squeeze the avocados out of their skins into a bowl, removing the stones. Add most of the chilli and coriander, the onion, tomato and lime juice. Mix everything up with a spoon, hacking up any bigger bits of avocado as you go. Have a taste to check the balance, and season with salt and pepper, if needed.
Put a griddle pan on a high heat to get nice and hot. There are two ways to prepare squid – choose whichever you prefer, or do both to get a feel for it. For both methods put the legs aside. The first way is to place a knife inside the tube and lay it on your chopping board, then score across the squid at ½cm intervals with a small sharp knife. The knife inside will prevent you from cutting all the way through so you’ll be left with ‘concertina’ squid. This method lets heat and flavours in and looks good. The second way is to put the knife in the tube and cut through the side, open it out then lightly score every ½cm in a criss-cross fashion with a blunt knife. This means the squid will curl up and absorb extra flavour.
Season the squid with a pinch of salt and pepper and drizzle with a little olive oil, then toss to coat. Add it to the screaming hot griddle, scored-side down, for 1 to 2 minutes (you may need to do this in batches). Use tongs to turn the squid over once it has nice char marks. Give it a minute on the other side until it curls up, then immediately transfer to a bowl and hit it with a lug of extra virgin olive oil, the lime juice and another small pinch of salt and pepper. The legs can stay on the griddle for a bit longer to get crispy.
Spoon the guacamole onto a platter. Cut the legs up a bit and add to the bowl of dressed squid. Cut the concertina and scored squid into bite-sized chunks. Pile the squid over the guacamole and drizzle with a little extra virgin olive oil. Scatter over the reserved coriander and chilli then tuck in.