Parboil the potatoes for 10 minutes and leave to cool. Peel and coarsely grate.

Mix in a bowl with the onion, Cheddar cheese and parsley. Season with salt and pepper then divide into 4 flattened patty shapes.

Heat half the olive oil and butter in a frying pan and cook 2 of the patties over a high heat for 1 minute, then reduce the heat and cook for 10 minutes, turning half way. Repeat for the other cakes.