Sally Clarke suggests making this the day before and reheating to serve straight from the oven. Like cooks and hosts, many dishes are more enjoyable when they’ve had some time to relax.
Root Vegetable Gratin
- 2 large Désirée or King Edward potatoes
- 2 large sweet potatoes
- 1 large celeriac
- 3 large parsnips
- 3-1/2 oz (100g) butter, melted
- 2 teaspoons finely chopped rosemary leaves
- 9 fl oz (250ml) double cream
- 4 fl oz (125ml) chicken or vegetable stock
- 3 bay leaves
- 2 garlic cloves, crushed
- sea salt and freshly ground black pepper
- Peel all the vegetables and rinse well with cold water. If you have one of those clever vegetable slicing machines, now is the time to get it out. Slice each vegetable and keep them separate so that the colours are not mixed up. Alternatively, cut the potatoes, sweet potatoes and celeriac in half and slice across as thinly as possible by hand, with a sharp knife. The parsnips may be sliced across whole, in thin slices.
- Choose an ovenproof dish that will hold all the vegetables and brush with half the melted butter. In a small bowl, mix the rosemary with 1 teaspoon of salt and 1 teaspoon of pepper. Start to fill the dish with the potato slices – they should be arranged in concentric circles so that they slightly overlap one another. Add a sprinkling of the rosemary mixture.
- Cover the potatoes with half the sweet potatoes in the same way, then add the celeriac, then the remaining sweet potatoes, then finally the parsnips. This final layer should be arranged as carefully as possible, with beautifully overlapping slices, as this will be the top of the finished dish.
- Preheat the oven to 180°C (160°C fan), 350°F, Gas mark 4. In a saucepan, combine the double cream, stock, bay leaves and crushed garlic with ½ teaspoon of salt and ½ teaspoon of pepper. Heat until simmering. Remove the bay leaves and set aside. Gently pour the liquid over and around the sliced vegetables, allowing each addition to slowly sink into the dish before adding more. You may not need all the liquid, but any leftovers could be used to top up the dish during cooking. Drizzle the remaining melted butter over the top and garnish with the bay leaves.
- Place the dish on a baking sheet (as the cream may bubble over while cooking) and bake for 1 hour–1 hour 20 minutes, or 10–15 minutes if reheating. If the surface of the gratin starts to colour too soon, simply cover with a piece of foil and continue to bake until a small sharp knife pierces the centre easily. The top should be golden brown all over, with a few crisp, slightly burnt edges for colour. Remove the dish from the oven and serve immediately, or cover tightly with foil to keep warm until you are ready to serve.