Salt-baking is a great way to cook both vegetables and meats whilst retaining their moisture. A simple paste of egg whites, salt and flour is wrapped around the food before baking it slowly at a moderate temperature - once cooked, the food is moist, tender and beautifully seasoned. Here, a whole celeriac (celery root) is baked along with a little fresh thyme and plenty of black pepper to create a hearty centrepiece of a dish, perfect alongside roasted game or simply served alone with a drizzle of truffle oil.
Scrub the celeriac under cold running water using a firm-bristled brush to remove any dirt. Dry it well. There is no need to peel the celeriac.
Mix the remaining ingredients into a dough and knead it for 2 minutes until it becomes slightly elastic.
Roll out the dough to approx. ¼ inch thickness. Place the cleaned celeriac in the centre of the dough and mould it up and around the celeriac, completely sealing it inside the dough. Make sure there are no holes in the dough - if so, pich them to seal.
Place the wrapped celeriac in the air fryer basket and bake at 350°F (180°C) for 50 minutes.
Once baked, remove the celeriac from the air fryer, crack open the top of the salt crust and add a knob of butter or a drizzle of truffle oil and freshly ground black pepper.