1. Combine onion, potato, mustard and ¾ of the cheese, crumbled. Mix well, season and then divide into 4.
2. Heat oil, add one quarter of the potato mixture and press into a 3”/7cm round, fry 8-10 minutes to golden, turning as you go.
3. You should be able to cook 2 at a time.
4. Keep warm whilst you cook remaining mixture, then serve hot with the remaining cheese crumbled on top.