To prepare the squid, lay the squid flat on a board. Insert a long, thin knife in the opening and neatly cut it along one side. Open it out to a flat sheet and scrape away any leftover membrane. Use the tip of the knife to lightly score the flesh in a diamond pattern, taking care not to cut through the squid completely. Cut the scored squid into large triangles ready to be floured and fried.
For the caponata, the aubergine needs to be cut into uniform dice: slice it lengthways about 1cm thick, cut long strips the same size, then chop them into squares.
Heat half the oil in a large saute pan. Fry the onions for 3-4 mins until starting to soften, add the aubergine, then continue to cook for 8-10 mins until brown and soft. Tip into a colander over a bowl.
Tip any oil from the bowl back into the pan and top it up with a splash of fresh oil. Fry the celery, tomatoes and the crushed garlic together. Sprinkle the sugar over, splash in the vinegar, then cook for 3-4 mins until the tomatoes start to release their juice.
Tip the aubergine and onion back in with the celery. Scatter in the olives, capers and basil, then give everything a good stir. Cook for 5 mins until simmering, then season to taste. Turn off the heat, drizzle in the rest of the oil, then set aside.
Just before cooking, tip the squid into a large bowl. Sift the flour and cayenne pepper together over the squid, then toss well and season with salt. Tip the squid back into the sieve and shake off all the excess flour.
Pour enough sunflower oil into a large frying pan so it’s about 1cm deep. Heat the oil until it sizzles when sprinkled with a little flour. In batches, fry the squid for 2-3 mins on each side until golden and crisp. When cooked, use tongs to lift the squid onto a plate lined with kitchen paper. You are now ready to serve.
Spoon the caponata inside a 10cm wide metal ring (or simply make a neat pile) in the middle of a medium dinner plate. Use the back of the spoon to press down lightly on the caponata and level the top of the pile. Carefully lift the ring away, keeping the tower of caponata circular. Lean five or six pieces of squid around the caponata like petals on a flower, then serve immediately.