Prawn

Nearly every failure is overcooking

Prawn protein finishes setting between 50 and 60°C, and the flesh is thin enough to get there in two or three minutes. Past that it keeps losing water and turns to rubber.

The point is that it does not reverse. An undercooked prawn wants thirty more seconds; an overcooked one has no remedy.

C and O

The reliable doneness signal is not colour, it is shape.

• Curled into a C — done. Take it out now.
• Curled tight into an O — overcooked.
• Waiting for it to go fully red is usually waiting too long.

In dishes where the prawn is the point — gambas al ajillo, shrimp scampi — that judgement is the whole recipe. In soups it is safer to cook them in the residual heat after the pot comes off, which is how tom yum goong and fish amok handle it.

Devein the back

The dark line along the back is the digestive tract. Harmless, but gritty and slightly bitter. It is more pronounced the larger the prawn, so remove it on big ones and do not bother on small ones.

Grilling in the shell, slit the back shallowly and lift it out with a toothpick. Cooking in the shell tastes considerably better — the aroma lives in the shells and heads, which is why a dish built on prawn flavour like paella either leaves them on or makes a separate stock from the shells (stock).

A short brine changes the texture

Fifteen minutes in brine — 500ml water, 1 tsp salt, ½ tsp sugar — then patted dry, gives noticeably firmer, springier flesh. Salt alters the muscle protein structure so it holds water, and the effect is largest on previously frozen prawns (salt and seasoning).

Beyond thirty minutes it turns salty and tough instead.

Frozen is usually the better buy

Prawns are commonly frozen on the boat within hours of being caught. The "fresh" prawns on a fishmonger's ice are often that same frozen product, thawed — in which case thawing them yourself is fresher.

• Thaw in the fridge overnight, or in a hurry, in the bag in cold water for twenty minutes.
• Hot water and the microwave cook the outside.
• Dry them completely after thawing or they will not sear — a wet prawn steams (freezing and thawing).

Dried shrimp and salted shrimp are different ingredients

Both carry the word "shrimp" and neither substitutes for fresh. They are savoury bases, and they do a different job in a dish.

• Dried shrimp — drying concentrates the savour. Grind it into a broth or a paste, the way it works in chipsi mayai style frying. A brief toss in a dry pan lifts the aroma first.
• Salted shrimp (saeu-jeot) — a salt-fermented condiment at 10-20% salt, so taste before you add any salt of your own. It is where much of kimchi's savour comes from, and it is the same thing served alongside suyuk. Put it where fresh prawns belong and the dish comes out salty with the ferment dominating.

Treat both as belonging with building umami and salt and seasoning rather than with fresh prawns.

Size codes

A label like "16/20" is the number of prawns per pound (about 450g). Smaller number, bigger prawn. When a recipe calls for king prawns it is also telling you the cooking time is longer, so smaller prawns need less.

Storing

• Refrigerated, one to two days is the limit. On ice, in the coldest part of the fridge.
• Judge by smell. Sea smell is normal; ammonia means throw it out.
• Peeled prawns spoil faster than shell-on.
• Save the shells and heads in the freezer — they are stock.