Kosher salt usually has no additives, and it has large, coarse flakes. A grain of kosher salt is composed of many salt crystals stuck together. With its large surface area, it can absorb more moisture than a similar sized table salt grain, and this makes kosher salt excellent for curing meats. That is where the name comes from. The salt itself is not kosher, but because it can draw out the last traces of blood from meats, this salt is used to make meat kosher.
Most gourmet chefs prefer cooking with Kosher salt to any other kind. The reason is that Kosher salt adds tremendous pure, clean, crisp flavor and allows them to better control portions with their fingers for seasoning and sprinkling. By nature of it's "flake" texture it melts easily and is less dense than table salt. Chefs also prefer Kosher salt because of its ability to dress up a meal for presentation. The large, irregular grains of Kosher salt add a delightful crunch and hit of briny flavor when sprinkled on food at the last minute.
Nutritionally, Kosher salt is no different than table salt, although it does not provide iodine.
Among its many uses:
Encrusting: Kosher salt can be mixed with water to form a thick paste to encrust both meat and fish. After baking, the salt crust is removed and discarded, leaving behind delicious and moist meat or fish. Coating a beef roast and letting it slowly cook for four to five hours will produce extremely juicy meat.
Brining: Soak meat in a bath of water and Kosher salt to add flavor and juiciness to meats and seafood. It's a wonderful way to produce an exceptionally moist, flavorable Thanksgiving turkey.
Flavor enhancer: Chefs like using Kosher salt because they feel it provides the cleanest, truest flavor. You can use Kosher as you would table salt in most cooking applications. Just remember that it does not provide iodine, a required nutrient which we mostly get from iodized salt.
Rub: Mix Kosher salt with spices and marinate meat or poultry in the refrigerator for at least 30 minutes. Then, bake, broil or grill to your desired tenderness.
Cocktail Glass Salt: Cocktails such as Margaritas and Bloody Mary's are traditionally served in a glass with a salted rim. Sprinkle Kosher salt on a plate. Moisten the rim of the glass with lime or lemon and dip the glass rim into the salt using a slight twisting motion. Lightly shake off excess salt.
If you don't have Kosher salt and need to subsitute, use coarse pickling salt which contains no additives and is roughly the same texture. You can also use non-iodized table salt but use half as much as the recipe calls for (table salt is more dense). Kosher salt adheres to the food better than table salt.