Good-quality balsamic vinegar and walnut oil make all the difference in this dressing. If you can find a roasted walnut oil, its intensely nutty flavor will not be overpowered by the rich balsamic vinegar. This vinaigrette is delicious paired with Heirloom Lettuce Salad with Strawberries, Walnuts and Goat Cheese, but it’s also light enough to dress delicate baby spinach or baby greens.
From The Earthbound Cook: 250 Recipes for Delicious Food and a Healthy Planet by Myra Goodman
Combine the vinegar, mustard, and both oils in a glass jar and seal the lid tightly. Shake the jar vigorously to combine. Season the vinaigrette with salt and pepper to taste. (The vinaigrette can be refrigerated, covered, for up to 1 month. Let it return to room temperature and shake vigorously before using.)