In a large saucepan, combine the potatoes and enough water to cover. Bring to a boil, salt the water and cook until tender, about 8 minutes. Rinse under cold water; drain well.
Season the chicken cutlets with salt and pepper. In a large nonstick skillet, heat a drizzle of EVOO over medium-high heat. Add the cutlets and cook, turning once, until golden, about 5 minutes. Transfer to a plate. Add the ham steak to the skillet and cook, turning once, until browned, about 5 minutes.
While the meats cook, grate the shallot into the bottom of a large salad bowl. Whisk in the mustard, vinegar and honey, then whisk in 1/3 cup EVOO. Season with the thyme, salt and pepper.
Cut the chicken, ham and swiss cheese into thin strips and add to the dressing. Add the celery root, carrots and potatoes. Toss to coat well. Divide the salad among plates garnished with the watercress leaves. Serve with the baguette and butter.