Foolproof Vinaigrette

1. Combine vinegar, shallot, mayonnaise, mustard, salt, and pepper to taste in small bowl. Whisk until mixture is milky in appearance and no lumps of mayonnaise remain.
2. Place oil in small measuring cup so that it is easy to pour. Whisking constantly, very slowly drizzle oil into vinegar mixture. If pools of oil gather on surface as you whisk, stop addition of oil and whisk mixture well to combine, then resume whisking in oil in slow stream. Vinaigrette should be glossy and lightly thickened, with no pools of oil on its surface. (Vinaigrette can be refrigerated for up to 2 weeks.)

LEMON VINAIGRETTE
This is best for dressing mild greens.
Substitute fresh lemon juice for vinegar, omit shallot, and add 1⁄4 teaspoon finely grated lemon zest and pinch of sugar along with salt and pepper.

BALSAMIC-MUSTARD VINAIGRETTE
This is best for dressing assertive greens.
Substitute balsamic vinegar for wine vinegar, increase mustard to 2 teaspoons, and add 1⁄2 teaspoon chopped fresh thyme along with salt and pepper.

WALNUT VINAIGRETTE
Substitute 1-1⁄2 tablespoons roasted walnut oil and 1-1⁄2 tablespoons regular olive oil for extra-virgin olive oil.

HERB VINAIGRETTE
Add 1 tablespoon minced fresh parsley or chives and 1⁄2 teaspoon minced fresh thyme, tarragon, marjoram, or oregano to vinaigrette just before use.