Button mushrooms are a field mushroom and are a younger form of flat mushrooms. Avoid withered, slimy, pitted, or bruised mushrooms. Button mushrooms are good when using whole or when a more delicate, subtle flavour is required. Store mushrooms in a paper bag in the refrigerator. Mushrooms are mostly grown inside and as a result quality is consistent all year round. However, mushrooms donâ€™t like the heat so quality can be diminished in summer.