Remove the bones from the fish using a peeling knife or tweezers.
Cut out two rectangles of greaseproof paper, slightly larger than the fish fillets. Place the fish on them, skin side up.
Mix the egg yolk with ateaspoon of water and apinch of salt. Spread this glaze over the fillets of fish on the skin side using a brush.
Peel the potatoes, wash them, and cut them into very thin slices. Shape them into scales using an apple corer.
Put the potato scales into a frying pan. Cover them with cold water, bring them to a boil, and continue to boil for 1 minute. Drain them.
Pour the “scales” into a bowl with the clarified butter. Mix. Add the potato starch. Mix carefully.
Arrange the scales over the fillets of fish, starting at the head and making them overlap one another. Leave in the refrigerator for 15 minutes.
Make the Sauce
Squeeze the oranges. Pour the juice into a saucepan with the rosemary and reduce it to dry* over medium heat. Add the Noilly Prat and reduce it the liquid by half. Work in the crème fraîche, 2 to 3pinches of salt, and pepper.
Allow the liquid to reduce by half, around 10 minutes over high heat, until the sauce has thickened.
Cook the Mullet
During this time, heat 2tablespoons of olive oil in a frying pan. Pick up each fillet, in the rectangle of paper (by hand). Turn it over in the oil. Take off the paper. Salt the flesh side of the fillets. Let them cook for 6 minutes over high heat, until the scales are a deep golden brown. Turn the fillets over and let them cook for a few seconds.
Strain the sauce. Coat the plates with sauce. Draw a few “scales” with veal stock, using a spoon.
Arrange the fillets on the plates. Add alittle chervil to garnish. Serve hot.