Potato and Mushroom Pie

Slice the button mushrooms and chop the onion.

Sauté the onion until golden brown.

Add the mushrooms, stir, and cook over high heat for about 7 minutes until most of the liquid evaporates, then remove from heat and let cool.

Stir flour, egg, and hard cheese into the mashed potatoes until you get a thick, dough-like consistency (add a bit more flour if needed).

Grease the inside of a baking dish with oil, transfer the potato mixture, spread it across the bottom, and form a small crust edge.

Whisk together the sour cream and egg, pour the mixture over the cooled mushrooms, season with salt and pepper, and stir everything together.

Transfer the filling into the potato crust.