Let's imagine that you are going to prepare leeks. There are thousands of ways to do it, but one of the most classic is "sautéed".
How do you do it?
- You peel, wash, dry and slice your leeks
- You do the same thing with a shallot
- In a saucepan or a frying pan, you heat a littleoil or butter or clarified butter
- Once it's hot, you pour in the shallot, stir a little and add a little salt and pepperHere is the first salt shaker, note that it is light, and concerns (for the moment) only the shallot, we continue...
- Cook the shallot, 1 minute maximum, it must not colour or turn brown (we say"without colouring")
- Add the leeks, stir well to mix, and do not add any salt.
Why not? Well, because the salt with its hygroscopic side, if you add it now, will "pump" the water out of the leeks, water that will end up at the bottom of the pan, and that you will have to remove later by overcooking.
Moreover, if the water is extracted from the leeks, they will become excessively soft and less appetizing, losing their beautiful green colour more easily. Let's continue... - You cook/sauté the leeks like this, uncovered, stirring from time to time, until they are soft to your taste, but still green
- And finally, off the heat, you add salt and pepper to taste
You will have understood, it is just a question of timing, we will salt anyway, but we will also try to do it late, so that the salt is not too much in contact with raw vegetables. This is valid for "soft" vegetables, but also for mushrooms.
By doing so, you will have a cooking that preserves the structure of the vegetable, and you avoid the excess of liquid at the bottom of your pan.
To sum up: When cooking vegetables or mushrooms, it is best to add salt only once the cooking is finished, to keep your vegetables in good condition.