Celery Root and Salt Cod Napoleon, Pickled Egg Yolk, and Confit Mushrooms
For the Salt Cod Béchamel:
Soak the salt cod in water overnight, changing the water often. Simmer the soaked cod in the milk with the onion, peppercorns, and porcini mushrooms over a very low heat until the cod easily flakes. Remove the fish and cool. Add the white roux and stir until you achieve a béchamel consistency. Season with salt and pepper and strain through a chinois. Remove any skin and bone from the cod and flake the flesh with a fork. Add enough béchamel to bind the cod and cool.
For the Celery Root:
Preheat the oven to 300°F. Line a baking sheet with a silicone baking mat and brush with butter. Put the celery root on the baking sheet and brush tops with more butter. Season with salt and pepper and sprinkle a few thyme leaves on each. Cover with a second silicone baking mat and bake until very tender but not brown. Remove from the oven and cool.
For the Pasta:
Make a pasta dough with the eggs, egg yolks, and flour. Roll the dough out and cut into 8-inch sheets. Blanch in salted boiling water and shock in ice water. Cut the pasta to the desired size and shape for napoleons and toss with olive oil to prevent sticking.
For the Confit Mushrooms:
Preheat the oven to 275°F. Combine the mushrooms, oil, thyme, and garlic in a pan and cover with foil. Cook in the oven for about 45 minutes. Strain the oil from the mushrooms and reserve.
For the Pickled Egg Yolk:
Crack the poached eggs into a bowl of cold water. Remove the whites and any membranes. Put the yolks in a small bowl and stir in the Sherry vinegar. Season with salt and pepper.
To Assemble and Serve:
Preheat the oven to 400°F. Layer the Pasta, Salt Cod Béchamel, and Celery Root 3 times over, finishing with a layer of Pasta. Bake until heated through and until the top layer of pasta has begun to crisp and caramelize. Meanwhile, heat some Confit Mushrooms with a small amount of the confit oil and stir in the freshly chopped herbs at the last minute. Plate a smear of the Pickled Egg Yolk, then plate the napoleon. Finish with the Confit Mushrooms.