Wash the mushrooms and cut into slices. In a pan put the oil and half the butter, chopped parsley and garlic in two parts. Heat the sauce well, do not fry, pour the mushrooms, turn them well and cover with a lid. As soon as they left their water, uncover and cook. If it's hard mushrooms (boletes, chanterelles, etc.) add a ladle of water and cook longer. When the water is all dried, salt and add the remaining butter.
Store the mushrooms in an airtight container in the fridge for 2-3 days at most.