You will need
Melt half the butter with half the oil in a non-stick frying pan. Grate in the potatoes then add the onion and salt and pepper to taste. Mix together. Press down well with a spatula.
Cover with a lid and cook over a moderate heat for about 12 minutes, or until the potatoes are golden brown underneath.
Turn the potato cake out upside down on a plate. Melt the remaining butter and oil in the pan.
Slide the potato cake back into the pan and cook the other side for another 12 minutes, or until golden brown.
cooking for one or two