Heat the clarified butter in a frying pan, brown the meat in batches for approx. 30 secs. each side, remove, season.
Finely chop the parsley, finely chop the onions and mushrooms.
Heat a little clarified butter in the same frying pan and sauté everything.
Add the lemon juice, season. Completely reduce the liquid and leave the filling to cool completely.
Halve the flaky pastry crosswise. Place 1 tablespoon of breadcrumbs and 1/4 of the filling in the centre of each section of dough.
Place the steaks on the sections of dough.
Beat the egg. Coat the edges of the dough with the egg, fold over and press down with a fork.
Place the pastry parcels with the seam downwards on a baking tray lined with baking paper.
Coat with egg and pierce several times.
Bake for approx. 20 mins. in the centre of an oven preheated to 200°C.