Place the celeriac in a saucepan of salted water and bring to the boil. Reduce the heat and simmer for about 20–25 minutes until really soft. Drain well and set aside.

Meanwhile, place the carrots and sweet potato in a separate saucepan of salted water and bring up to the boil. Reduce the heat and simmer for about 20 minutes until completely soft. Drain well and set aside.

Tip the cooked celeriac into a food processor, add the crème fraîche, nutmeg, salt and ground black pepper, and blend until really smooth (you could also use a hand-held stick blender).

Meanwhile, return the carrots and swede to the saucepan and blend to a smooth purée with a hand-held stick blender, or use a food processor. Stir in the butter and season to taste.

Serve both purées separately while they are still hot.

Mary’s tips: The celeriac purée can be made the day before and reheated in a buttered dish covered in foil in a hot oven. Not suitable for freezing.