Truffled celeriac purée

serves 6 The celeriac is baked in a salt crust until tender, before being whizzed into a purée. This can be made the day before and reheated when you want to serve. If you do this, just add the truffle at the last minute. 800g strong flour, plus extra for dusting 400g table salt 7 egg whites

2 medium celeriac heads, scrubbed well and any small roots removed 1 egg yolk, beaten, for brushing 300ml double cream 1 small black winter truffle, chopped, or 1 tbsp black truffle oil To make the salt-crust dough, place the flour and salt in the bowl of a stand mixer. Turn the mixer on and add 200ml cold water then the egg whites. Mix for 2-3 minutes then turn the machine off and scrape down the sides of the bowl. Continue to mix until the dough comes away from the bowl.

Split the dough into two pieces, wrap in cling film and chill for 20 minutes in the fridge.

Preheat the oven to 180C/gas mark 4.

Roll out each piece of dough to a large round on a floured surface, about 5mm thick. Place a celeriac in the middle of each dough circle and gather up the dough around it to cover the celeriac completely.

Brush the edges of the dough with the egg yolk and pinch together at the top to seal. Turn each parcel over and place on a heavy-duty oven tray. Bake for 50 minutes. Remove from the oven and leave to cool for an hour, then carefully remove the top of the crust with a knife.

Scoop out the baked celeriac, place the flesh in a pan with the cream and bring the mixture to the boil. Season to taste. Remove from the heat, place in a jug blender and blend until smooth. Pass through a fine sieve.

Add the chopped truffle or oil and serve.