Potato, leek and sauerkraut gratin

Sauerkraut brings a welcome acidity to a rich potato gratin. This is a relatively easy side dish, and it reheats well, too.

Prep 20 min

Cook 1 hr 50 min

Serves 6




Ingredients:

15g unsalted butter

1 tbsp olive oil

600g leeks (ie, about 3 large ones), trimmed, cut in half lengthways, then cut into 4cm lengths

Salt and black pepper

1 tbsp thyme leaves, roughly chopped, plus 4 extra sprigs

4 garlic cloves, peeled and crushed

200ml double cream

200ml whole milk

300g sauerkraut, store-bought or homemade

20g chives, cut into 1½cm lengths

1kg maris piper potatoes, peeled and cut into 1cm-thick rounds

150g gruyère, roughly grated

Method

Heat the oven to 200C (180C fan)/390F/gas 6. Put a large, ovenproof saute pan for which you have a lid on a medium-high heat, and add the butter and oil. Once hot, add the leeks, a quarter-teaspoon of salt and plenty of pepper, and cook, stirring occasionally, until the leeks have softened and are just beginning to colour – about eight minutes. Add the chopped thyme and garlic, cook for two minutes more, until fragrant, then turn off the heat and leave to cool slightly, for 10-15 minutes. When the leeks have sat for 10 minutes, put the cream, milk and 200ml water in a small saucepan on a medium heat, bring to a gentle simmer, and keep warm on a low heat.

Stir the sauerkraut, chives, potatoes, half the cheese, three-quarters of a teaspoon of salt and a generous grind of pepper into the cooled leeks, and smooth out the top so the potatoes are lying flat. Pour over the warm cream mixture, then sprinkle on the rest of the cheese and top with the thyme sprigs. Cover the pan, bake for 50 minutes, then remove the lid and bake for 30 minutes more, or until golden and bubbling. Leave to rest for about 15 minutes before serving directly from the pan.