A pat of butter
Chopped fresh parsley
Catsup--just a small shot
Walnuts, finely chopped
Once again, I'm giving you a recipe with no measurements. That's because I gave away the cookbook that I got this recipe from and have made it ever since using approximate amounts.
Melt the butter over medium heat in a saucepan and add some finely chopped white onion and the chopped mushroom stems. Cook until the onions are transparent, then add the bread crumbs. These are the kind you make yourself from stale bread, not the kind you buy prepackaged, which are too fine for this recipe.
When the crumbs have browned somewhat, remove the pan from the heat. Add the remaining ingredients in amounts that make sense to you. You can add salt and pepper to taste, if you wish.
Place the mushroom caps, topside down, in a greased baking pan. I've read somewhere that life is too short to stuff mushrooms, and that's true, so just pour the "stuffing" over the mushroom caps.
Bake at 350 for 10 minutes or until the mushrooms are tender.