Step 1

Preheat the oven to 190°C and grease a 1.5-litre baking dish. Place the cream, garlic and thyme in a pan and bring to just below boiling point, then stand for 15 minutes to infuse.

Step 2

Meanwhile, very thinly slice celeriac and potato (a mandoline is ideal). Toss celeriac and potato together, then layer in the greased baking dish, pouring over some cream mixture, drizzling with a little truffle oil and seasoning between each layer, until you have 6-8 layers. Scatter the cheese on top.

Step 3

Cover with a layer of baking paper and a layer of foil, then bake for 45 minutes. Remove the paper and foil, then bake for a further 15 minutes or until tender, bubbling and golden.