To Eat or Not To Eat?

There is a lovely colony of white large mushrooms out in my raised bed and into the grass. I pulled this on up and laid it with some holey  Swiss chard in case I could sauté it for supper.
But I only eat supermarket mushrooms and am not sure about the safety. They look safe, like white Portabellas. But what do I know?
I think my mother's old adage: "when in doubt, throw it out."
Now that it is pouring down rain all the time I am not inclined to go out to the garden to pick any more.
They is the first time I have ever had mushrooms show up in my garden.
What do you Fungus Blippers think?
Extra is another angle.