Peel and dice sweet potatoes in 1/3 inch cubes. Heat a large frying pan and add the oil, butter, and onion. Saute for a few minutes until the onion is clear, then add the cinnamon and allspice, salt, and pepper. Add the diced potatoes and saute until lightly browned. Toss with the parsley just before serving. Good recooked like hashbrowns.