1. Wash, peel and rewash the potatoes.
2. Place into a saucepan, cover with cold water, add a little salt and bring to the boil.
3. Turn down the heat and simmer gently until only just cooked.
4. Drain in a colander, refresh under cold water and allow to dry.
5. Peel and finely slice the onions and chop the parsley.
6. When the potatoes are cold, cut into half lengthways.
7. Heat a heavy-based frying pan over a medium heat and add enough oil to shallow fry the potatoes.
8. When the oil is hot, carefully lay the potatoes into the pan and fry until golden brown on the bottom. Turn the potatoes over and do likewise on the other side.
9. At the same time, heat a little oil in a smaller frying pan, add the sliced onions and fry until a light golden brown.
10. Remove the potatoes from the pan and drain in a colander, Shake to remove any excess oil.
11. Add the fried onions to the potatoes and mix together well.
12. Correct any seasoning and spoon the Lyonnaise potatoes onto a warmed serving dish or onto warmed plates.
13. Sprinkle chopped parsley over the Lyonnaise potatoes and serve immediately.