Nigella Lawson served up tasty chip gratin with Swedish ansjovis (sprats) for the festive season on Nigella’s Cook, Eat, Repeat: Christmas Special.

The ingredients are: 60g butter, plus extra for greasing, 2 large onions, approx. 400g/14oz, thinly sliced, 2 tsp sea salt flakes, plus ½ tsp (or 1 tsp fine sea salt, plus ¼ tsp), 1.25kg potatoes, peeled and cut into narrow strips like French fries, black pepper, 2 x 125g tins Swedish ansjovis (sprats), drained, 300ml full-fat milk, 300ml double cream and 2–3 tbsp breadcrumbs (optional).

See recipes by Nigella in her book titled : Cook, Eat, Repeat: Ingredients, recipes and stories. available from Amazon now.