I have spent some time experimenting with different types of prawns / shrimp. I started with those peeled ones that come out of the freezer cabinet of the supermarket but (a) they are not all peeled, so some shell is left, and (b) they have that thin black line down the back which is the intestine and must be removed (it is not dangerous, just unpleasant).
So, you pay around €5 for 200g of large prawns and cook them from frozen and then have to de-vein them (take out the thin black line), which is very time consuming, before eating them. But there is another way, go large! In every Spanish supermarket they offer larger shell-on prawns which are raw and (although previously frozen) are sold at the fresh fish counter. The prawns are measured by the number per kg, so 14/16 is roughly the number you will get per kg.
Although these seem to be much more expensive, maybe €10/kg, they actually offer much better value in the weight of prawn meat you get per € and they taste very much better than the ready-peeled variety. Spend the same money as you would have before on peeled prawns (and buy just 500g for two people), if still frozen, allow to defrost in the fridge. So now we get into recipe mode, something I have never done before.
While still raw, shell the large prawns, you will find that almost none need de-veining; the vein comes out when you tear the head off. Put all the heads and shells in a saucepan and bring another saucepan of salted water to the boil. Cook the bodies of the prawns for as short a time as possible, until they have gone pink, maybe only 60 seconds depending on their size, immediately remove from the heat, drain and plunge into a bowl of iced water. You now have really fabulous top-quality prawns that can be used with a marie-rose sauce (mayonnaise, tomato ketchup, pepper, lemon juice and a little Tabasco– experiment to see what you like). This mixture goes well with avocado or as a luxury prawn cocktail.
Now to the free lunch.
Cover the heads and shells of the prawns with water and boil for an hour.
Take off the heat and liquidise, I use a hand blender but any form of kitchen gadget that chops them up small is fine.
Boil for another hour to concentrate the flavour and reduce the liquid.
Sieve into a smaller saucepan to remove the shells.
Add a little tomato puree, some cream or crème fraiche, a good dash of Tabasco, ground pepper and a teaspoon of maize flour dissolved in an eggcup of brandy.
Back on the hob, whisk until it comes to a simmer and thickens.
To be extra-delicious, you can add some raw prawns at this stage which starts the whole process again!
This may seem like a long process but the actual time needed at the cooker is less than 15 minutes (you don’t need to be present while the shells are boiling). Result, something as good as lobster bisque and free! The prawn meat that you have extracted from the shells is more that the defrosted ready-peeled bag of prawns (much of which is water), the taste is far better, hardly any de-veining is needed and you get a fabulous soup for free.