Heat half the olive oil in a paella dish or heavy-based saucepan. Add the chorizo and pancetta and fry until crisp. Add the garlic, onion and pepper and heat until softened. Add the thyme, chilli flakes and calasparra rice, and stir until all the grains of rice are nicely coated and glossy. Now add the paprika and dry white wine and when it is bubbling, pour in the hot chicken stock, add the chicken thighs and cook for 5-10 minutes.
Now place the clams into the dish with the join facing down so that the edges open outwards. Sprinkle in the peas and chopped tomatoes and continue to cook gently for another 10 minutes.
Meanwhile, heat the remaining oil with the garlic cloves in a separate pan and add the prawns. Fry quickly for a minute or two then add them to the paella. Now do the same with the squid and add them to the paella too.
Scatter the chopped parsley over the paella and serve immediately.
If you don't have a pan large enough to hold all of the rice and paella ingredients, use two pans and divide the rice between them.