1. Keep the stock ready.
2. Peel and finely slice the onion.
3. Wash, peel and rewash the potatoes and cut into thin round slices.
4. Keep them in cold water until required.
5. Lightly grease an ovenproof dish with a little butter.
6. Pre-heat the oven to 180°C (Gas Mark 4).
7. Place a layer of sliced potatoes into the bottom of your dish.
8. Next, add a layer of sliced onions and season with salt and pepper.
9. Add another layer of potatoes and onions and season.
10. Top with a neat layer of sliced potatoes and season.
11. Pour the stock over the layers of potatoes until it just covers the top layer.
12. Add a knob or two of butter.
13. Place into the pre-heated oven and cook for about 1 ½ hours or until the potatoes are cooked and most of the stock has been absorbed.
14. When the top layer of potatoes are a nice light golden brown, cover the dish with a lid or foil to prevent any further cooking.
15. Before serving your boulangere potatoes, brush melted butter over the top layer of the boulangere potatoes and sprinkle over a little chopped parsley.