Scrub sweet potato and regular potatoes; dice into cubes and place in a large pot of boiling water and boil until tender (about 15-20 minutes).
Meanwhile, in a large skillet, cook beef and onion until meat is no longer pink; drain. Add the corn, peas, carrots, tomato sauce, Worchestershire sauce and spices. Place in a 1-qt baking dish coated with cooking spray; set aside.
Drain the potatoes and place in a large mixing bowl. Mash with butter, milk, salt and pepper. Spread evenly over meat mixture.
Bake, uncovered at 350 degrees for 25-30 minutes or until heated through.