Dijon substitutes the salt in this recipe, making for stronger vinaigrette that goes well with steamed vegetables such as cabbage or leeks. This will make enough for one medium-sized head of lettuce or a vegetable dish for two people; increase ingredients proportionally for larger salads.
Pour vinegar into a bowl, add Dijon mustard, and whisk together. Once a creamy consistency is reached, slowly whisk in olive oil. Whisk together until combined. Add tarragon and then toss with salad or serve as a sauce over steamed vegetables.