<table> </table> A bottle of olive oil, a cruet of vinegar, a dish of sea salt, a pepper grinder. This is the simple formula for vinaigrette, a sauce so humble that it often doesn&#8217;t seem like a sauce at all.</p><p>But it is. In French, it&#8217;s called <em>la sauce vinaigrette.</em> A good one transforms a bowl of salad into something extraordinary.</p><p>And it&#8217;s not just for salads. A drizzle of vinaigrette on the plate can elevate any number of dishes: grilled fish or roasted chicken, pan-seared steak or wilted greens.</p><p>As the weather warms and diners crave simpler fare, grilled outside or fresh from the market stands, a vinaigrette can be all we need or want.</p><p>It&#8217;s the simplest thing in the world to make. Just memorize this: 3-to-1. That&#8217;s the classic proportion of oil to vinegar.</p><p>Because there are so few ingredients, their quality is important. Use the best oil and vinegar you can find, good sea salt and freshly cracked black pepper.</p><p>The only equipment needed is a whisk and a bowl. Whisk the salt and pepper into the vinegar first, because salt doesn&#8217;t dissolve in oil, but it does in vinegar. Then whisk in the oil. That&#8217;s a basic sauce vinaigrette.</p><p>A classic vinaigrette is made with red wine vinegar and olive oil. Add to it mustard or shallots or herbs or spices. And vary the oil and vinegar by using walnut or hazelnut oil, balsamic or white wine vinegar or sherry vinegar.</p><p>Traditionally, the oil is drizzled in slowly and whisked all the while to emulsify it, resulting in a creamy, smooth sauce. Whisk a little Dijon mustard into the vinegar before the olive oil and it emulsifies even more easily. (If using an amazing olive oil, though, skip the mustard, which will cover up the nuances of the oil.)</p><p>But you don&#8217;t have to emulsify: Everything will combine when you toss the salad. Or, if you&#8217;re using the vinaigrette to sauce a plate that will receive a fillet of sole, you might welcome the amber beads of olive oil eddying in the rosy vinegar, the oil and vinegar beading and traveling on the plate like a pointillist painting.</p><p>Depending on the oil and vinegar and your palate, you might want to depart from the basic 3-to-1 ratio. Vinegar can vary in acidity from 4 percent to 8 percent or more.</p><p>For a high-acid vinegar, use closer to 4 parts oil to 1 part vinegar. Ditto if substituting lemon juice for some or all of the vinegar or to highlight a great olive oil.</p><p>A softer vinaigrette, made with a higher percentage of a particularly floral extra virgin olive oil, perfectly complements a delicate salad of butter lettuce and fresh herbs.</p><p>A sharper vinaigrette, with a higher proportion of, say, aged balsamic vinegar, would accompany grilled steak or a salad of wilted bitter greens: dishes that can stand up to, or even call for, a more pronounced flavor.</p><p>A mustardy vinaigrette is great with seared flank steak or wild salmon.</p><p>Experiment with flavors by matching mild rice wine vinegar with a touch of toasted sesame oil added to the olive oil, or pair walnut oil with mellow sherry vinegar.</p><p>Play with texture. Chopped basil, a fine dice of shallots or a mash of roasted garlic adds not just flavor but body. Whisk in grated ginger or stone-ground mustard and wild honey.</p><p>Playing with temperature is an option, too. Heat the vinegar or use pan juices in place of some of the oil to make a hot vinaigrette, a simple and fast sauce to complement the roast chicken or pan-seared hanger steak.</p><p><hr class="infobox-hr-separator" /> <div class="infobox"> <strong><span class="infobox-head">Butter lettuce and spinach with citrus and avocado </span></strong><br /> Makes 4 to 6 servings</p><p>1 head butter or bibb lettuce