How to Make a Perfect Salad

A fresh-tasting salad of varied greens is one of summer's most magnificent offers. And it demands so little of us.

For most people there is cooking, and there is salad. Although many of the things we do in the kitchen are complex and fraught with uncertainty, salad seems to be a worry-free endeavor. There is little or no measuring of ingredients, no catastrophe that looms if you do not keep track of time or temperature. Salad is just a bunch of leaves, perhaps with vegetables or something more substantial, such as cheese, thrown in, tossed with a dressing.

Here is where it gets complicated: Salad hates dressing, and dressing hates itself.

Let me explain. The greens we use in salad, whether or not they come from the lettuce family, are tender leaves with a shiny, waxy layer on the outside and thin cell walls within. The cells should be packed with moisture, enough to make the cell walls burst when we bite into them, creating the characteristic crunch that most people appreciate.

If you were to wash the leaves with soap, it would remove their protective layer, and they would end up dry and limp, their fresh hue replaced by a dull darkness. Although most of us would never think of washing salad with detergent, the dressing ingredients we most commonly use have much the same effect.

Sprinkle a little lemon juice or vinegar on a salad leaf, and watch it wilt. Even more dramatic is the effect of oil, the other principal ingredient in most dressings. You would think that oil would protect the poor, fragile leaves; instead, it helps dissolve the waxy outside. It seeps into the interior, leaving the leaf unprotected, slowly drained of moisture.

That does not mean we should stop using oil or vinegar or change the way we make salad. We just need to understand the principles at work; otherwise, we may inadvertently ruin perfectly good food. Salad is, and should be, something we assemble at the last minute, without thinking too much about it.

That is useful to bear in mind when you are cooking for important occasions. All too often, salads at big dinners are drab affairs because there was too much early prep. When a salad is assembled in advance, the result is a dramatic loss in freshness. But as long as we toss the salad just before it is served, as we would with any weekday dinner, we're fine.

Salad leaves are most happy when they are kept cool and moist. Then they are the way we like them best: bursting with water, their crispness not just palpable but audible. (Eating salad should be a noisy affair.) Have you ever picked salad greens in the early morning hours, when they are still covered in dew, and then sampled leaves from the same plant later in the day? It is hard to believe they are one and the same.

Keeping a salad fresh is the challenge. Modern packaging has done much to improve the shelf life of salad greens, but it can slow the effect of time for only so long. The minute the greens are picked, they start losing moisture. After a few days in the fridge or an hour or so in the car on the way back from the store, the leaves become limp and unappealing. Luckily, as long as the plant structure has survived, that process is reversible. A few minutes in ice water will, through the magic of osmosis, reinvigorate the leaves. Because normal tap water is not very cold at this time of year, I either use refrigerated water or add a few ice cubes to the water. (I do that before I add the greens and then stir well; that prevents freezer burn, which might occur if ice straight from the freezer is dumped directly onto the delicate leaves.)

As for dressing, to say that it hates itself is not an exaggeration. Most classic dressings -- not only vinaigrettes, but also thick, cheesy Caesar salad dressings -- consist of fat, in the form of oil, and water, in the form of vinegar or lemon juice. Normally, oil and water will do anything to stay out of each other's way. If you combine oil and vinegar in a glass, you can whisk the two together. But leave the mixture for a few seconds and it will separate into two layers, the oil on top and the vinegar on the bottom. A dressing that separates will leave parts of the salad covered in oil, other parts in vinegar: one part fatty but bland, one part just plain angry.

The trick is to make the two come together in an emulsion, just as when making a mayonnaise or hollandaise. Luckily, that is much easier with a dressing than with the classic French sauces. All you need is an emulsifier. Add a teaspoon of mustard or egg yolk (or both, as I do with Caesar salad), stir or shake vigorously and you will have a thick dressing that coats the salad leaves evenly, with all the flavor components in each drop.

If you insist on making an ultra-simple vinaigrette with nothing but oil and vinegar, you should thoroughly chill the ingredients beforehand; when cold, even an unstable emulsion will stay combined longer.

Bottled dressings fall outside normal categories, as most of them are stabilized with starch or gums and are a different entity altogether. Although commercial techniques vary, I find that most store-bought dressings just don't taste fresh. Why pay the food industry to make something that I can whip up at home in 30 seconds?