Whole roasted celeriac in porcini butter

Method

1. Put the dried porcini in a jug and add just-boiled water to cover, then set aside for 5 minutes. Drain through a sieve (reserving the liquid) and put in a food processor with the garlic and half the herbs. Pulse until finely chopped, then add a drizzle of oil (or truffle oil) and most of the butter. Season well, then whizz until combined.
2. Heat the oven to 190ºC/170ºC fan/gas 5. Pierce the celeriac all over with a paring knife. Put 2 large pieces of foil on top of each other, then put the celeriac in the middle. Rub the celeriac all over with the porcini butter, working it into the nooks and crannies. Wrap the foil tightly around the celeriac (see Make Ahead), then put the parcel in a snug ovenproof dish and roast for 2 hours or until the celeriac is tender all the way through.
3. When there are 30 minutes of cooking time left, make the sauce: put a large frying pan on a low-medium heat. Add the remaining butter, a drizzle of oil and the chopped shallots, then cook gently for 10 minutes. Finely chop the remaining herbs and add to the pan.
4. Once the shallots are ready, add the torn mushrooms, turn up the heat and fry for 10 minutes until golden. Add the brandy and fry until the alcohol has almost cooked away, then add the stock and a splash of the porcini soaking liquid. Bring to the boil, stir in the crème fraîche, then season well with salt and black pepper.
5. When the celeriac is almost ready, open up the foil and baste the celeriac with the buttery juices. Return to the oven, leaving the foil open, and cook for 10 minutes to turn the top golden brown.
6. Put the celeriac on a platter, pour over the juices and serve in slices. Stir the parsley into the sauce and serve on the side.