What are open cup mushrooms?

Open cup mushrooms, commonly referred to as "open cap" or "open cup" varieties, are characterized by their umbrella-shaped caps that are not fully closed over the gills. This allows for easier spore dispersal and often results in a more pronounced, exposed gill structure. Popular examples include the common button mushroom (Agaricus bisporus) in its mature form, as well as portobello mushrooms. They are widely used in culinary dishes for their flavor and texture.