Begin by bringing a pan with 1 pint (570 ml) of water to simmering point. If using raw prawns, drop them into the water for 3 minutes. After that, remove them with a draining spoon, reserving the cooking liquid. (Cooked prawns will not need this pre-cooking.) Now set aside two whole prawns and shell the rest. To do this, just remove the heads by giving them a sharp tug, then simply peel off the rest - which comes away very easily - but leave the tails intact as this makes them look nicer. Now remove the black vein from the back of each prawn, which will come away easily using the point of a sharp knife. Next place the shells in the pan of water and simmer for 30 minutes, without a lid, to make a nice prawn-flavoured stock, then drain and discard the shells. Pour the hot stock into a jug and cover with a plate to keep warm.
Now heat the frying pan over a high heat and brown the pieces of chorizo sausage, without adding any fat, then remove them from the pan to a plate and set aside. Then add a tablespoon of the oil and, when it's hot, fry the onions for 2-3 minutes to brown them a little at the edges, then return the chorizo to the pan and add the garlic, celery, chilli and sliced pepper. Continue to fry for 4-5 minutes, till the celery and pepper are also softened and lightly tinged brown at the edges, adding a little more oil if you need to.
Now stir in the rice to get a good coating of oil, then measure out 12 fl oz (340 ml) of the reserved stock and add the Tabasco to it. Next add the chopped tomatoes and bay leaf to the pan, then pour in the stock. Season with salt and freshly milled black pepper, give it all one stir and push the rice down into the liquid. Now turn the heat to low, put a lid on and let it barely simmer for 20 minutes.
Then, check the rice is cooked and return the shelled and the two reserved shell-on prawns to the pan, adding a little more stock if necessary. Cover with a lid for 5 more minutes, then serve garnished with the chopped parsley and spring onions.