
This elegant celeriac roast dinner turns a humble root vegetable into a rich, deeply caramelized centerpiece. Served with silky creamed celeriac and a savory onion-thyme gravy, it is a satisfying vegetarian alternative for Sunday lunch or a holiday table.
Peel the celeriac, reserving the skin for the gravy. Cut a thick 8-10 cm steak from the middle of the celeriac and set the remaining pieces aside. Put the celeriac steak in a saucepan, cover with cold salted water, bring to a boil, then reduce to a gentle simmer and cook for 12 minutes. Lift out the steak carefully and reserve the cooking liquid.
Heat the oven to 200C/180C fan/gas 6. If you like, lightly score both flat sides of the celeriac in a criss-cross pattern. Melt the butter in an ovenproof frying pan over medium heat, then brown one side of the celeriac steak for about 10 minutes until deeply golden. Turn it over, drizzle with the maple syrup, tuck the thyme around the pan, and transfer to the oven. Roast for about 1 hour 30 minutes, basting every 20 minutes and turning twice, until glossy, darkened, and tender all the way through.
While the celeriac roasts, make the creamed celeriac. Cut the reserved celeriac pieces into chunks and return them to the reserved cooking liquid. Bring to a boil, then simmer for about 10 minutes until very soft. Scoop the celeriac into a bowl, add the creme fraiche, and mash until smooth or blend for a finer puree. Season with salt, cayenne pepper, and a little grated nutmeg, then set aside and reheat before serving.
For the gravy, finely chop the reserved celeriac skin. Melt a little butter in a frying pan, then cook the celeriac skin, onion, bay leaves, and thyme for about 15 minutes until well browned. Stir in the light brown sugar and cook until caramelized. Add the flour and cook for 1 minute, then stir in the Marmite and tomato puree to make a thick paste. Splash in the red wine vinegar, pour in about 400 ml of the reserved celeriac cooking liquid, add the stock cube, and season with soy sauce to taste. Simmer until thickened, then strain into a clean pan or jug.
About 10 minutes before serving, gently reheat the creamed celeriac and gravy. Bring the whole roasted celeriac to the table and carve into thick slices, or cut into quarters. Serve with the creamed celeriac and gravy, then finish with a few thyme leaves and finely grated chestnut, if using.
For a smoother mash, blend the cooked celeriac with a hand blender instead of mashing by hand. If the gravy gets too thick, loosen it with a splash of the reserved cooking liquid. Leftovers keep well in the refrigerator for up to 2 days and can be reheated gently on the stovetop or in the oven.