DRESSING: Combine all ingredients in a glass jar and shake. SALAD:In large skillet over high heat, saute meat in butter, a few cubes at a time until browned on all sides. Transfer to a large bowl and cool. Quickly saute mushrooms in remaining butter and add to meat. Add artichoke hearts, celery, tomatoes, chives and parsley. Mix lightly. Mix dressing with mustard. Pour over salad, toss, cover and marinate overnight.