Tiger prawns, or shrimp as Americans call them, are crustaceans with a brain the size of a pinhead, even though the bigger prawns may weigh up to 56.7gr. when cleaned. They are priced by how many prawns make up a pound after the head is removed. The most expensive are "Under 8," which means no more than eight prawns to a pound. The smaller sizes really are tiny and are up to 50 or more prawns per pound. Larger sizes are better for grilling. Smaller sizes work in casseroles.
Defrost the prawns by placing them in a colander under cold running water. It shouldn't take more than two or three minutes even for the large prawns to defrost.
Hold the prawn in your non-dominant hand with the legs facing downward. Slit the back of the shell with the knife. Remove the black or dark brown vein you see with the tip of the knife. That's the intestines. If you leave it in it won't hurt you but it's not appetizing to know it's there. Leave the shell on the prawn. Rinse the prawn and place in a bowl.
Chop the cilantro, jalapeño, garlic and the white and light green part of the scallions finely. Add 1 tbsp each of lemon and lime juice.
Press back the shell of the prawns and stuff in the herb mixture in between the shell and the prawn meat. Put the prawns in the bowl and add another tablespoon each of lime and lemon juice.
Heat the grill to medium.
Pierce the prawn as close to the fat end, where the head used to be, with one skewer. Pierce it again about an inch away toward the tail end with another skewer. Using two skewers prevents the prawns from flipping around on the skewer.
Place the prawns on the grill, one to two minutes per side--exactly how long depends on how big the shrimp is and how hot the grill. Test a prawn for doneness by cutting into it. It should no longer be translucent but a white opaque colour. The shells should be bright pink. Cook a minute or two longer if the prawns aren't done.
You can sauté prawns in a skillet instead of grilling them. Plan on 0.113kg. to 1/2 lb. of shell-on prawn per person.
Overcooking prawns makes them dry and gives them a mealy texture. They also shrink in size the longer they cook.