Favorite salad of my household. It is ideal with roast meat and barbecue. And in a very easy to prepare. Wash the mushrooms, slice them and cook in salt water. In the meantime, onion cut into pins, and squeeze a little hands and a cup of clean to let the juice. It is more tasty salad when you have young onions and when the green part of the slice. Strain the mushrooms. When cool, mix with onions, sour cream and mayonnaise.