I am not surprised you answered first. We are in the west Michigan woods and have many kinds of mushrooms. I know them pretty well after 35+ years here. Forgot to mention that when fully open caps are close to 4” in diameter. Looked through our 2 mushroom books and went to google images searching under white mushrooms. I was stumped so I turned here.
I hope that someone recognizes this mushroom. The thing about mushrooms is that although many are delicious, some are poisonous. It’s important to be cautious.