Instructions

1. For the walnut pastry: Sift the flour and salt into a large bowl. Rub in the butter with your fingertips until the mixture resembles coarse breadcrumbs.
2. Stir in the walnuts and sugar and add enough beaten egg (probably half an egg) just to bind the mixture together. Pull together with your fingertips.
3. Preheat the oven to 190°C.
4. Press into a 23cm square tray, score the desired shape onto your pastry before chilling for 20 minutes to 1 hour.
5. Bake on the top shelf of the oven until lightly golden and cooked through. Remove to a wire rack to cool.
6. For the celeriac purée: Juice the lemon. Peel the celeriac and cut it into 5cm chunks. Submerge the celeriac in cold acidulated water.
7. Peel the potatoes, cut into chunks the same size as the celeriac and put them into a small saucepan. Cover the potatoes with salted water, bring to the boil, then lower the heat and simmer until tender.
8. Put the celeriac chunks in a separate saucepan, cover with salted water, add a little lemon juice and bring to the boil. Reduce the heat and simmer until tender.
9. When the vegetables are cooked, drain well, keeping them separate and allow to steam dry in colanders for a few minutes. Mash the potato by pushing through a sieve with a spoon. Mash the celeriac by blending in a food processor. Combine the two vegetables in a saucepan.
10. Over a gentle heat, stir in the cream with enough milk to reach your desired consistency. Stir in the butter and allow to melt. Season well with salt and pepper.
11. For the yolks: Heat a water bath to 60°C. Weigh each egg and write the weight in grams on each one. They will cook for 1 minute per gram. Place the eggs in their shells into the water.
12. Set a timer and remove eggs when appropriate in accordance with each weight.
13. When the eggs have cooled down, peel them and separate the white from the yolk. Place the yolks into a lightly oiled bowl to store until ready to plate.
14. For the mushrooms: To cook the mushrooms, heat a large non-stick sauté pan over a medium heat and add a few tablespoons of olive oil. When the oil is hot, add the mushrooms and season well. Cook for 4-5 minutes, occasionally shaking the pan so that they colour evenly. Add the chopped parsley, garlic and a squeeze of lemon juice, cook a little longer and remove from the heat.
15. To assemble, place a piece of pastry on a plate, topped with celeriac puree, a spoon of wild mushrooms and an egg yolk. Drizzle with a little truffle oil and serve with your choice of microherbs, if desired.