This was a staple in our family. It was a good way to use up left over mashed potato... but these days I actually make more than enough mashed potato just so I can make these the next day. They can be served with either jam/jelly, a sprinkling of sugar or have them savory with nothing on top. They are best eaten as soon as they are out of the pan as they harden up once they go cold but a quick nuking in the microwave oven and they are almost as nice as they are fresh.
If you are using cold left over mashed potato you will need to moosh it up again so it will mix in well with the other ingrediants. Slightly beat the egg and add it to the potato. Sift on the flours and salt. Knead together just enough to mix all the ingrediants.
Heat oil up in a pan. I usually pop a small amount of cold oil into a bowl so I can oil my hands as I take small amounts of the Potato batter and roll in a ball, flatten by patting between hands and slip into the hot oil. The Patty should be about 1cm (1/2 inch) thick when you pop it into the hot oil. It will puff up and when it is amedium brown flip it over. Do not have the oil too hot other wise it will just burn and not cook through... but if you have the oil not hot enough it will just soak up the oil... it is basically trial and error but do test drops with small pieces. It should take only a min or so on each side to cook.
Drain on paper before serving. As kids we ate this with Jam or sprinkled with sugar but the adults had it savory with dilled pickles or olives. My Australian sister inlaw grates some cheese into the batter and adds some chives to it. She has even diced some ham and onions in it too... It is very diverse. If there was no left over mashed potato I have even gone as far as just nuking some potatoes in the microwave whole, in their skin... then scooping out the insides of the potato to make these pancakes.