Heat olive oil in a skillet while you assemble your potato cake mixture. Watch the oil very carefully, and do not let it smoke. Remove it from heat immediately if you see that it is getting too hot. In a large mixing bowl, place the mashed potatoes, beaten egg, flour, dried onions and parsley. Mix well. When the oil in your skillet is hot, spoon a portion of the potato mixture into the hot oil. It should sizzle nicely. Continue the spooning of the potato mixture until you fill the skillet or run out of mixture. Smooth out each potato cake into roughly a circular shape. Check for brownness on the under side of each potato cake, and when it is brown to your liking, turn and brown the other side. When each potato cake is done, remove it from the skillet to a platter topped with a paper towel for draining. Then move all potato cakes to a serving dish. Garnish with parsley, if you like. I think you will love this comfort food