Boil the potatoes and fry them with 1 diced onion to roast potatoes.
Clean the mushrooms, cut them into small pieces and sauté with the second onion. Salt and pepper a little. Fry the chicken breast fillet or turkey breast fillet and also season with salt and pepper.
Put everything in layers in a round, greased casserole dish, starting with the fried potatoes. Then put the mushrooms and finally the fillets on top. Pour the hollandaise sauce over them.
Baked in a preheated oven at 180 ° C for about 30 minutes.