Knead the crushed potatoes with 50 g butter, egg yolk, salt, nutmeg, cheese, 30 g flour and breadcrumbs to a firm dough.
Roll out two round dough bases, place one of them in a buttered baking dish.
Finely chop the mushrooms, dice the bacon and peeled onions.
Sauté the bacon and onions in 30 g hot butter until translucent, add the mushrooms and cook covered for approx. 10 minutes. Then dust with 40 g flour and stir in the cream. Bring to the boil briefly, season with salt and pepper.
Pour the mixture onto the dough base in the baking dish, cover with the second dough base. Pierce small ventilation holes and place the pie in the preheated oven.