Langoustines look a lot like crayfish, but come from salty seas and oceans rather than fresh water. A relative of the lobster, langoustines grow to about 10 inches in size but are most prized when smaller, because the meat is sweeter. You cook this luxury ingredient much in the same way that you do lobster -- steaming, boiling or roasting. They may also be deep-fried or grilled, or their meat can be used as an ingredient in mixed seafood recipes.
When a langoustine dies, the flesh immediately deteriorates and becomes inedible if not preserved. You'll most often find langoustines frozen, as they are challenging to keep alive once caught, so fishing vessels immediately quick freeze them. Fresh langoustines are transported in individual compartments because they can't be in contact, or they might die. This complexity ups their price and exotic factor. The shellfish is available whole, broken down into tails or as chunks of meat. Never refreeze thawed langoustines; you'll toughen the meat and increase the chance that the meat could become contaminated with bacteria.
Large langoustines can be cooked just like lobster. Cut them in half, brush the meat with melted butter and herbs -- fresh tarragon is especially nice -- and bake or grill them. Boil smaller specimans in heavily salted water and serve with lemon butter or garlic mayonnaise for dipping. If you're using frozen langoustines, just run them under cool water for 10 minutes to defrost them.
Poach small, sweet tails can in garlic butter to create a decadent scampi. Quickly saute them in olive oil, garlic, chili flakes and fresh parsley. Serve over thin pasta noodles or alone, with French bread and a salad on the side.
Chopped langoustine meat may be added to any dish that calls for seafood, including some curries and paella. Boil the meat briefly to warm it and add to a salad with a vinegar-based dressing. Mix chopped langoustine meat with other minced seafood, and use it to fill ravioli or to create a stuffing for flounder or another white fish.