Lasagne sheets with celeriac sauce, olive tapenade and egg yolk

Method

1. Turn the oven to 70°C fan/gas 1⁄4 and pour the olive oil into a small ovenproof saucepan or dish. Put the pan/dish in the oven while it heats up. Once it’s reached the full temperature, wait 5 minutes, then carefully add the yolks to the oil. Return to the oven for 30 minutes.
2. Peel the celeriac and slice thinly, then chop into small pieces. Put the celeriac in a saucepan, cover with the stock and simmer for 15-20 minutes until completely soft (the time will depend on how finely you sliced the celeriac).
3. Meanwhile, make the tapenade. Put the olives, anchovies (if using), mustard, parsley and 1 tbsp olive oil in a food processor. Pulse into a coarse dressing (you can also do this by hand by finely chopping the ingredients and mixing them together). Taste and season with salt, pepper and lemon juice, then add a little more oil if needed to make a dressing loose enough to drizzle. Set aside.
4. Strain the celeriac (reserving the stock), then put in a blender with the butter and parmesan. Whizz, adding the reserved stock as needed, until you have a smooth, silky sauce with the consistency of single cream. Taste and season with salt and the cider vinegar, then return to the pan and keep warm over a very low heat.
5. Bring a pan of salted water to the boil. Cut the pasta sheets into large, randomly shaped pieces, about 4-5 shapes per sheet (use a fluted pasta wheel if you have one). When the celeriac is soft, add the pasta to the water and cook for 2-3 minutes.
6. Drain the pasta and add to the celeriac sauce, tossing to ensure the sheets are covered. Divide among 4 plates, creating a little well in the centre. Use a spoon to carefully lift the yolks out of the oil and place one in each well. Drizzle over the tapenade and serve immediately, with a crack of black pepper, more parmesan and a final drizzle of oil (you can use the oil the yolks were cooked in). The yolk should be broken and stirred through the dish at the table.