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.