Raw or cooked prawns — which should I buy?

Almost all prawns sold in UK supermarkets, raw or cooked, have been frozen at some point and often thawed for the counter. That is not a mark against them — freezing at sea is how prawns stay good. What matters for your dish is whether the protein has already been through its one and only cooking.

Step by step

1. Work out whether heat will touch the prawn.This is the whole decision. If the prawn ends up hot, buy it raw. If it ends up cold, buy it cooked. Everything else is detail.
2. Buy raw for any cooked dish.A raw prawn goes from translucent grey to opaque pink in about two minutes and stops there. You control that moment. It also releases flavour into the pan, which a cooked prawn cannot do because it already gave it up to whoever cooked it.
3. Buy cooked for cold dishes and for speed.Prawn cocktail, sandwiches, salads, a cold noodle bowl. Cooked prawns are also the sensible answer when you need something on the table in five minutes and are willing to accept firmer texture.
4. If a recipe uses cooked prawns hot, add them last.Off the heat, or in the final thirty seconds, purely to warm them through. Any longer and they tighten into rubber. Never simmer cooked prawns in a sauce.
5. Check whether they are 'previously frozen'.Most counter prawns are thawed. That is fine, but it means you must not refreeze them raw. If you want the flexibility, buy the frozen bag instead and take out what you need.
6. Read the size code rather than the adjective.'King' and 'jumbo' are marketing terms with no fixed meaning. A count per kilo or per pound on the pack is the real size measure — a lower count means bigger prawns.

Common mistakes

• Using cooked prawns in a curry or stir-fry — You are cooking them a second time. They shrink, tighten and go rubbery, and they give the sauce nothing because their flavour went into somebody else's cooking water.
• Judging size by the word on the front of the pack — 'King prawn' is not a regulated size. Two packs both labelled king can differ by half again in weight per prawn. The count per kilo on the back is the honest number.
• Refreezing thawed counter prawns — They were frozen at sea and thawed for display. Freezing them again costs a lot of texture, and the pack will normally say do not refreeze for that reason.

Alternatives

• Frozen raw shell-on: The best value and the best result for cooking. The shells protect the flesh in the freezer and make a good stock. Thaw in the fridge or under cold running water in a sealed bag.
• Frozen raw peeled: Convenient and only slightly inferior. Pat them very dry before cooking, because peeled prawns carry a lot of surface ice glaze that otherwise floods the pan.
• Chilled cooked and peeled: For cold dishes only. Convenient, expensive per kilo of actual prawn, and impossible to improve.
• Cold-water prawns: Small, sweet, almost always sold cooked, and much better in a sandwich or cocktail than a large warm-water prawn. Different product, not a lesser one.

Questions people ask