Unroll the puff pastry. Cut the ham into small slices. Cut the puff pastry into 16 triangles. Put about 1 tsp of bechamel sauce on the base of each triangle.
Sprinkle some grated cheese on top of the bechamel and then add ham slices on top. Preheat oven to 350°F (180°C).
Roll each triangle starting rolling from the base to the top of the triangle. Press each side to give them the croissant form.
Put the croissants on a baking tray topped with a baking sheet and then baste some egg yolk on top of each croissant.
Bake your croissants for 20 minutes at 350°F (180°C).
