Will save and try your recipe, but the mushroom at the Drake was probably baked, maybe broiled. I have no memory of the taste, as I do remember the taste of my Great-grandmother and Great-aunt's recipes, but I do remember that I was upset that I had not ordered it, and it may have been the most delicious thing I had ever eaten.
I did not see your post until just now. I do use the stems in my recipe for small stuffed mushrooms; crisped bacon, cheddar or American cheese, and chopped up stems dotted with butte, topped with crumbs if desiredr; very tasty, but not approaching what I tasted at the Drake, if memory serves me well. Nothing in my repertoire even approaches what was in that dish. In my very young mind the mushroom was huge; the sides came up around the filling UNnlike a Portabello. Is my memory flawed or is there such a mushroom?