Boil the potatoes and peel them. Heat the butter and add the julienned chicken meat. Braise until golden. Clean the onion and mushrooms and cut them into suitable pieces. Add them to the meat and fry until they soften. Season with salt and black pepper.
Sprinkle with flour and stir. Add the milk and cream in a thin trickle while stirring nonstop. Cook another 2-3 min.
Pour the mixture into an oven dish. Bake in a preheated 356°F (180 °C) oven for about 20 min. Take the oven dish out and sprinkle the dish with grated boiled potatoes and grated cheese.
Finish baking another 10 min. Sprinkle the ready dish with chopped parsley at the end.