A friend recently told me that every ingredient should be salted as it is added to a dish when cooking. Really!?--Lynn
Cooking is full of a lot of myth and pretense, and perhaps even a little interference from special interests, and salt seems to be one of the big ones, nowadays (see Salt [of the Earth], and Fixing Over-Salted Food).
I have two major problems with this particular fad. First, and I think foremost, is that most of us are already getting way too much sodium in our diets. It makes food taste better and we need salt as part of our diets, but the USDA Dietary Guidelines suggest that we should limit our consumption of salt to less than 2,300 milligrams (mg) per day, if we are under 51 years of age, and 1,500 mg if we are older. 2,300 mg is the amount of sodium in only one teaspoon of table salt. The lesser amount, 1,500 mg, is just less than 2/3 of a teaspoon. And that is sodium from all sources consumed throughout the day, including not just the salt you sprinkle on, or the salt in packaged foods, but also sodium in the baking soda or powder used to make cookies, biscuits, cakes, etc.. At present, the average American gets about 3,400 mg of sodium a day, or about half again the maximum recommended amount. Adding salt at each step just increases the chances that you will have way too much salt in the final product, from both the health and flavor points of view.
Second is simply, can you tell the difference? Here is the experiment to construct. Cook two identical versions of the same dish, one where the salt is added at each step, and one where the same amount of salt is added at one time, preferably toward the end of preparation. Now have a bunch of friends taste the two dishes, without knowing which is which, and preferably mixing it up so some start with dish "A" and others with dish "B". If you have enough tasters and they can consistently tell which is which, then go with that. My bet is they won't know the difference, particularly on longer cooked dishes like stews.
There are reasons, however, why you might want to salt a particular ingredient. If you are making caramelized onions, for instance, some salt at the start of cooking helps to draw out water and soften the onions faster. Salt also draws water out of eggplant (aubergine) and cucumbers. In the case of eggplant, it can significantly change the texture, too. Salting meat may help encourage the Maillard reaction, creating a more flavorful dish. There is at least one dish I cook where I deliberately under-salt during cooking and then add salt at the table because it brightens the flavor.
Used strategically, salt enhances flavor and texture, helps in preserving, and speeds cooking. Used recklessly, it can ruin the taste of food and be a contributing factor in health problems.
If you feel you must salt at every step, then don't just throw salt in from your salt shaker (cellar, box, pig, ...). Instead, read the recipe, measure out the total amount of salt beforehand, and then use small pinches from the pre-measured amount. If there recipe doesn't provide a total amount, or says something like "Salt to taste", then you need to use your judgment, but you would still be wise to pre-measure the amount of salt you intend to use. In either case, aim to use half to two-thirds the salt you have set aside so you have some left over at the end to adjust the seasoning once the dish is complete.