The cap of the Parasol Mushroom, Macrolepiota procera, is oval when young and then broadly convex in age with a brown nipple at the center. It's very soft and has brown scales. The close, crowded gills are white when fresh, brown in age. The cap of the first one pictured here is 5.5 cm across. The long and slender stalk is 5 mm wide and around 12 cm long. The stalk has brown scales like the cap and a detachable ring. The stem tends to bend over in age. The one in the second photo can be seen in the background of the first. The spore print is white, an important detail since the similar (and poisonous) Green-spored Lepiota, Chlorophyllum molybdites, has greenish spores. This mushroom also somewhat resembles Amanita thiersii, minus the obnoxious odor. Always check for a volva at the base. You can see in the last photo where I dug around the base and saw nothing.
This mushroom is edible and quite good, but it is not a beginner's mushroom. There are many white cap-and-stem mushroom, and some of them are poisonous. Compare with the American Parasol.
The spores were 15 μm across.