Select vegetables according to season, personal preference and complementarity of colors, textures and tastes. Cut into very fine julienne by hand or shred fine in food processor, using shredding disc.
Whisk egg yolks, lemon juice, mustards, salt and pepper in medium bowl until well blended. Add oil, drop by drop, whisking continuously, until mixture is thick. Then continue whisking in oil in slow steady stream. Stir in vinegar.
To serve, pour amount of dressing desired over julienned vegetables in bowl; toss gently. Line individual salad plates with romaine, endive and watercress. Top with dressed vegetables, dividing evenly. Sprinkle with sprouts.
** Some vegetables to consider: carrot, zucchini, red, green, and yellow bell pepper, celery, celeriac, summer squash, chayote, Chinese cabbage, daikon, black radish, turnip, white and red cabbage, cucumber, tomato, sugar snap peas, broccoli stems. Julienned vegetables can be prepared ahead; refrigerate, wrapped in plastic wrap. Make dressing just before serving. Use one cup of julienne vegetables per person.