This classic, comforting and impressice French potato side dish makes a beautiful addition to Christmas dinner.

Ingredients

• 2 tbsp olive oil
• 2 onions, thinly sliced
• 4 garlic cloves, thinly sliced
• 1 tbsp finely chopped fresh thyme leaves
• 1kg/2lb 4oz medium-sized Maris Piper or Desirée potatoes, peeled and thinly sliced using a mandolin or sharp knife
• 80g/2¾oz butter
• 400ml/14fl oz vegetable stock
• 75g/2¾oz gruyère, grated
• salt and freshly ground black pepper

Method

Heat the oil in a frying pan over a medium heat. Add the onion, garlic and thyme and season with salt and pepper. Cook for 10 minutes, stirring often, or until just softened and lightly golden.

Place the potatoes in a large bowl and season with salt and pepper. Stir in the onion mixture.

Preheat the oven to 200C/180C Fan/Gas 6. Take a small slither of the butter and grease a 26cm/10½in deep round baking dish. Positiion the potatoes and onions on their sides in a circle around the outside of the dish, then add more circles inside until you get to the middle– they should be packed in snuggly.

Pour over the stock and dot over the rest of the butter. Cover tightly with kitchen foil and bake for 45 minutes or until the potatoes are soft and cooked through.

Turn the oven up to 220C/200C Fan/Gas 7. Remove the foil and scatter over the cheese. Bake for a further 10–15 minutes or until the top is golden and crispy.

Serve immediately.