To make the mayonnaise, mix the mustard and egg yolks in a bowl, then add salt and pepper. Next the oil needs to be added, but very slowly, so that the mayonnaise does not split. Finally add a dash of tarragon vinegar.

Grate the celeriac into a bowl, then add the mayonnaise, which should be just enough to bind the celeriac together.

For the ceps salad, place some vegetable oil in a heated pan, then add the ceps and season with pepper. Next add the sliced onions, parsley, chives and a dash of vinegar. Toss all the ingredients together in the pan and then place on top of the celeriac remoulade. Scatter walnuts over the top and drizzle some walnut oil over the dish. Finally, sprinkle some cracked pepper on top.