Creamy Celeriac Gratin

A little untraditional for your Christmas dinner, who says we have to be conventional? We love earthy, peppery celeriac slowly cooked in a creamy, cheesy bake with thinly sliced potatoes.

1kg potato, peeled and thinly sliced
1 celeriac, peeled and thinly sliced
1 onion, peeled and sliced
1 garlic clove, peeled and crushed
1 knob of butter
284ml Jersey double cream
200ml Jersey whole milk
50g parmesan or your cheese of choice, grated
1 teaspoon wholegrain mustard

1. Preheat the oven to 200°C/180°C fan/Gas mark 6.
2. Place a deep casserole dish on the hob and lightly fry the onion and garlic in the butter for a few minutes.
3. Add the sliced potatoes and celeriac and generously season.
4. Whisk together the milk, double cream, mustard and half the parmesan before adding to the dish.
5. Smooth the layered mixture over and sprinkle with the cheese.
6. Bake for 1 to 1 ½ hours until the cheese is golden and bubbling and the veg is soft and cooked through.