Instructions: 1 Preheat the oven (gas mark 7 / 425F / 220C). Meanwhile, peel and wash the potatoes, then slice them in rings. Peel the onion and slice it, also in rings.

2 Heat the oil in a frying pan, and fry the onion rings until golden.

Season.

3 Put a layer of potatoes in a greased ovenproof dish, followed by a layer of onions and another of potatoes. Add the knobs of butter. Season, pour in the wine. Bake for 1 hour.

The word "boulanger" ("baker") comes from "boulenc" in the Picardy dialect, meaning "maker of balls of bread".

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