Cut the mushrooms into quarters and fill them with cold water. The water level is two fingers above the level of mushrooms. And bring to a boil.
Salt the mushrooms literally by a pinch, as the cheese can give sufficient salinity. When the mushrooms are cooked, add milk to the pan. We cut the potatoes (I cut them into eights). And leave to boil.
While the soup is cooking, prepare the saute. Fry finely chopped onions and carrots in vegetable oil.
Add the roasting to the soup and cook until the potatoes are ready. And at the very end, add the melted cheese to the soup, stirring until it dissolves. I cooked a little after the soup was ready to make it a little thicker.