Heat oil in skillet and fry potatoes until light brown and soft. Drain on paper towels. Butter and 8 inch skillet. Add potatoes to cover the bottom of the skillet. Beat the eggs, parsley, onion, salt and pepper. Pour egg mixture over the potatoes and fry over moderate heat for 4 mintues. Cover the skillet with a plate during this cooking. Turn pie over onto plate then slide back into the skillet to brown the other side. Cover with the plate. Cook for 4 minutes. Cut into wedges and serve.