Begin by making the tomato sauce. Put the onion into a saucepan with half the oil and let it sweat slowly over a low-medium heat for around 15 minutes until it's soft (do not allow it to colour). If it looks as though it might catch, add a splash of water to the pan

Add the tomatoes and season with salt. Leave to simmer over a low heat for about 45 minutes, until the tomatoes are thick and rich, adding a little water if the level of the liquid gets too low. Remove from the heat

Put the remaining oil in another pan with the garlic and cook over a low-medium heat. When it's almost golden brown, add the basil leaves and stir. Pass the oil through a sieve into the cooked tomato sauce

Whisk the sauce to break up the tomatoes. If it's too thick, thin it with a little water, ideally some pasta cooking water. Pass the sauce through a wide-holed sieve resting over a bowl, and use the back of a ladle to extract the smooth mixture. Check the seasoning and add more salt if necessary

Preheat the oven to 200°C/gas mark 6

Blanch the peas in boiling water for 30 seconds, then drain well

Put 8 of the squid and the egg whites into a food processor and pulse until they are roughly chopped. Add the peppers, blanched peas and chives and continue to pulse until you have a coarse mixture

Use this mixture to stuff the remaining calamari, keeping some space free at the top. Place a piece of the tentacles at the end of the filling and close the calamari with a rosemary sprig or a toothpick

Trim the other end of each calamari to create a tiny hole and keep the filling from bursting out when cooking

Heat a large heatproof baking dish over a medium heat and fry the garlic in 1 tablespoon of olive oil. Add the calamari and fry for a couple of minutes until browned, then pour in the wine and let it evaporate over a medium-high heat

Add 400ml of the tomato sauce and the fish stock, then transfer to the oven for 20 minutes. You can check the filling is cooked through by sticking a toothpick in the centre of the filling; it should feel hot when you touch your lips. Serve immediately