Cut the onion into small cubes, cut the champignons into slices and chop the greens finely. Grate the cheese on a coarse or fine grater. Preheat the oven to 180℃.
To knead the dough, mix butter, sour cream and a pinch of salt in a deep container. You can use a mixer. Gradually add flour and knead the dough.
While the dough is resting, fry the onion over medium heat in sunflower oil for a couple of minutes. Then add the mushrooms and fry the contents of the pan for another 5-8 minutes.
To season the pie, combine sour cream, eggs and salt in a separate container. Mix well. You can use additional spices if you wish.
Roll out the dough to about 0.3 cm, line it in a mold, forming high sides. Place the mushroom filling and pour the sour cream mixture over it. Sprinkle chopped herbs on top.
Place the pie in the preheated oven and bake for 40 minutes. Five minutes before cooking, sprinkle generously with cheese and return to the oven.
When serving, decorate the pie with herbs or beautiful sliced vegetables. If served in portions, you can top it with sour cream or tomato sauce.