Scrub the celeriac to make sure it's really well cleaned as you don't peel it.
Take a large piece of aluminium foil. Put the celeriac in the middle, drizzle with the olive oil, season with a little salt and pepper and sprinkle over the thyme and the 2 whole cloves of garlic. Wrap the celeriac up well.
Cook it for 2 hours in the oven at 180C until it is soft all the way through.
While the celeriac is cooking, cook the pearl barley.
About 30 minutes before the celeriac is ready, cook the onions gently with a little olive oil until they are soft then add the crushed garlic.
Cook for about a minute before adding the mushrooms and the curry powder.
Add the stock and turn up the heat a little. Let it simmer until the liquid has almost disappeared.
Stir in the yoghurt and cooked pearl barley at the end.
Nutritional information is approximate and a guideline only.