To divide the puff pastry in 3 pieces, to cover with the transparent film 2 pieces and to stretch the third piece in a strip of the thickness of 1 mms. To put the strip on the floured table and to sprinkle half of it with the leaves put to 1 cms of distancefrom the one to the other. To press every leaf to its place with the fingers. To brush the other half puff pastry with little water and to refold it on the leaves, pressing with the palm of the hand to remove the air. To cross again the puff pastry refolded through the rolls of the machine to get a thickness of 1 mms, with a sharp knife to cut puff pastry in square of 5 cms for side. To continue to exhaustion of the pasta and the leaves. To loosen the butter to middle fire in a frying pan with heavy fund. To add the shallot, the salt and trufflen about for 2 minutes to let become the shallot transparent. To remove the frying pan from the fire. To put the lasagnas in 3 liters water in ebullition with 1 teaspoon and 1/2 of salt and to cook. Drain and to pour in the frying pan with the shallot. To mix gently and to serve well warm.