This is a favorite dinner for my Wife and me.
Fresh frozen. Flour, egg wash, coat with panko crumbs, into a med-hot CI skillet. OO, butter, 1 tbs lemon juice, 1 tsp minced garlic, cook 90 secs / side ( any more and it gets tough ).
The large mushroom is stuffed with diced green onions and Swiss cheese. I made a dip of Ranch dressing and Tabasco, wasn't necessary, but it was very good.