The most surefire way to make a thick, well-emulsified vinaigrette is to first whisk together the vinegar or lemon juice and the seasonings (salt, minced shallots or other members of the onion tribe, and mustard) in a small bowl. Then slowly add the oil, drop by drop, whisking as you go, until the dressing begins to thicken. Add the oil in more of a steady stream as the dressing becomes noticeably thicker. An alternative, and perhaps more convenient, technique is to place the vinegar or lemon juice and seasonings in a small jar with a tight-fitting lid and shake to blend. Then add the oil in three or four additions, shaking vigorously between additions. A third and equally popular method is to mix the vinegar and seasonings in a blender and then add the oil in a slow, steady stream with the machine running.
Vinaigrette can be stored, tightly covered, in the refrigerator for up to 2 weeks. Always whisk dressings briskly just before adding them to salads so that the ingredients are well mixed and in balance, and donΓÇÖt add more vinaigrette than is necessary to lightly coat the salad.
