First make a large quantity of clarified butter. Heat the unsalted butter on very low heat until it has completely melted but is not bubbling. Remove the egg whites with a slotted spoon. Leave to settle and drain carefully, so that the rest of the egg whites remain in the cooking pot. Leeks: cut the leeks 'into tagliatelle' and saute them in a few spoons of clarified butter.

Buttermilk mousseline: boil floury potatoes and spin them through the passe-vite. Make a not too thick puree with butter, egg yolks, pepper, salt and nutmeg. Dilute with buttermilk to a smooth mousseline. Make mini fries. Cut potatoes into 2 to 3 mm thick slices. Then cut them into mini cubes or sticks. Fry these 'smallest fries in the world' like normal fries, only with shorter baking times. The fish: lay the skrei, pre-portioned, completely submerged in the clarified butter, heated to 90°C. Add bay leaf, thyme, rosemary, pepper and salt. Leave to simmer for 20 minutes. Then check the cooking. Carefully remove the fish from the butter and place the slices centrally on the plates. On the plate: a bed of leek glaze with a fish leg on top, covered in clarified butter. Place a spoonful of buttermilk mousseline on both sides of the fish steak and in line with it. Place a tuft of leek shoots on the fish and finish the plate with a few spoonfuls of mini fries, scattered randomly.