Salt and pepper the loin roast all over, fry quickly on both sides in hot oil, immediately lift out of the pan and set aside. Cut potatoes into slices and fry in hot butter on both sides, lift out, pat dry with kitchen paper and salt. For the filling, finely chop the smoked meat, cleaned mushrooms and onion, heat the butter in a frying pan and lightly fry the chopped onion in it. Add the mushrooms and roast until there is no more liquid. Then mix in the smoked meat, season with parsley, salt and pepper and leave to cool. Butter an ovenproof dish and roll out puff pastry so that both the dish can be completely lined with it and there is still enough pastry left for the lid and any decorative strips. Line the mold with puff pastry, cover the bottom with half of the potato slices, place the lung roast on top and spread with the prepared stuffing. Spread the remaining potato slices over the stuffing and finish with the pastry lid, which can be decorated with pastry strips as desired. Brush the dough with egg yolk and bake in a preheated oven at 180 °C for about 45 minutes until golden brown. We recommend bacon green beans and tomato salad as side dishes.