From America's Test Kitchen
Vinaigrettes often seem a little slipshod—harsh and bristling in one bite, dull and oily in the next. We were determined to nail down a formula for the perfect vinaigrette, one that would consistently yield a homogeneous, harmonious blend of bright vinegar and rich oil in every forkful.
For starters, top-notch ingredients are crucial. Balsamic vinegar works best with more assertive greens. Fruity extra-virgin olive oil is preferred as an all-purpose oil option, while walnut oil is best for nuttier vinaigrettes. As for mixing methods, whisking together the ingredients only gets you so far. A key ingredient—mayonnaise—is necessary to emulsify (bind together) the oil and vinegar for a stabilized, smooth dressing.
Makes about 1/4 cup, enough to dress 8 to 10 cups lightly packed greens
It is important to use high-quality ingredients in this recipe. This dressing is best on mild greens. For a hint of garlic flavor, rub the inside of the salad bowl with a clove of garlic before adding the lettuce.