Prepare potato salad. Cover and chill until ready to serve. Prepare Lemon Vinaigrette and set aside until ready to serve. Plate salad. Prepare tuna.
Scrub potatoes with a vegetable brush under cold running water. Cut crosswise into 1-inch coins. Place potatoes in medium saucepan and add water to cover. Heat to boiling, then reduce heat, cover and simmer until potatoes are tender, about 5 to 10 minutes. Drain potatoes and set aside.
In large bowl, whisk together olive and canola oils, vinegars, mustard, shallots, herbs, salt and pepper and Worcestershire sauce. Add to potatoes and toss gently to mix. Cover and chill until ready to serve.
Lemon Pepper Vinaigrette:
Place all ingredients except oils in blender and blend to mix. With motor running, gradually add oils until incorporated.
To plate salads:
Toss watercress with lemon Pepper Vinaigrette.
On each of 4 large plates, arrange ½ a tomato, 1 egg, ¼ of the haricots verts, ¼ of the olives, ¼ of the dressed watercress and ¼ of the potato salad.
Sprinkle tuna pieces with lemon pepper seasoning and salad.
In large skillet over high heat, heat the 1 tablespoon olive oil. Add tuna and sear no more than 1 minute on each side. Slice against the grain into ¼-inch slices and arrange on prepared plates.
Nutritional Analysis per serving: 1205 calories, 45 g protein, 49 g carbohydrates, 93 g fat (69% of calories from fat), 274 mg cholesterol, 9 g fiber, 1052 mg sodium