I found a recipe on an index card in a vintage cookbook. Haven't tried it yet, since Mom is anti-mushroom. Just putting it in here so I don't lose it.
Ingredients:
12 large mushrooms
1 tbs minced onion
1/4 c butter
1/2 tbs salt
1 c soft bread crumbs
1/4 c grated parmesan cheese
Stove Top Dressing
Instructions:
Chop stems. Mix all together with Stove Top Dressing. Put in a shallow pan with a little water.
Bake at 400 degrees for 20-25 minutes.