Cooking such a pie will require some skill from you, but it will certainly meet your expectations. The main thing is to choose the right bone and prepare the cheeks.
Peel the onion and cut into cubes. Finely chop the white mushrooms. Use two forks to shred the meat.
Heat the pan and fry the onion until soft, add the mushrooms and meat, cook for 3 minutes. Pour in the demiglace sauce and cream and cook for 10 minutes. Salt and pepper.
In two deep refractory plates, place a bone in the center. Spread the filling around. Roll out the puff pastry a little, cut in half and cover the filling. Brush the dough with beaten egg. Put the plates in the oven, preheated to 180 ˚С and bake for 10-13 minutes, until golden brown.
Grease the finished pie with melted butter.