Watercress and Leek Salad

Pull watercress leaves from stems. Rinse leaves well and pat or spin dry. Reserve stems for another use or discard. Tear watercress leaves into small pieces and place in salad bowl. Split leeks lengthwise and then slice into thin half-moons. Rinse well in a bowl of cold water, letting sand settle to the bottom; repeat until very clean and then pat dry. Add to the bowl with the watercress. Sprinkle the herbs, salt and pepper onto the vegetables in bowl and toss well to combine. Refrigerate to chill lightly. At serving time, combine vinegar, mustard, oil and garlic in a small jar. Seal and shake until well blended. Pour over salad, toss again and serve.