Season the cutlets on both sides with pepper, marjoram, salt and thyme. Then turn them in the flour on the other side, shake well so that just a touch of flour sticks to the meat.
Fry the chops in the hot fat, at a good temperature for two minutes on each side. Remove the chops, set aside.
In the same frying pan, in the remaining parsley, fat, saute onion, ham and mushrooms until soft. Season well with salt and freshly ground pepper, dust with the remaining flour, stir, add cream and cook well.
Divide the rolled out puff pastry into rectangles a little more than twice the size of the cutlets. Place a cutlet on one half of each pastry piece, spread the surface of the meat thickly with the ham-mushroom mixture. Brush the edges of each piece of dough with egg white, fold the second half of each piece of dough over the cutlet. Then use a fork to press the edges of the dough well together so that nothing can spill out during baking(*).
Place the puff pastry cutlets on the baking sheet rinsed with cold water and brush with egg yolk. Meanwhile, bake in a well-heated oven at a good medium heat for about twenty-five minutes.
(*) The cutlets wrapped in puff pastry in this way can be prepared a little in advance, even the day before: cover with aluminum foil and refrigerate with the lid closed.