2 onions, thinly sliced
few thyme sprigs
2 tbsp olive oil
1 ½kg floury potato, such as Maris Piper or Desirée, peeled and sliced thinly, by hand or using a food processor
425ml vegetable stock

Heat oven to 200C/fan 180C/gas 6. Fry the onions and thyme sprigs in the oil until softened and lightly coloured (about 5 mins).

Spread a layer of potatoes over the base of a 1.5-litre oiled gratin dish. Sprinkle over a few onions (see picture, above) and continue layering, finishing with a layer of potatoes. Pour over the stock and bake for 50-60 mins until the potatoes are cooked and the top is golden and crisp.

Lighter and healthier than Dauphinoise and just as impressive, perfect for a cold winter's night