I got this recipe many years ago from one of my co-workers who was a vegetarian and a really good cook. Neither of us are still at the hospital where we once worked, but I still make his recipe from time to time -- it's a great appetizer, and very quick and easy to make. Depending on the size of your mushroom caps (and how many mushroom-lovers are in your crowd), plan on 2 - 3 mushroom caps per person. You can also make this ahead and then just pop them in the oven to bake when your guests arrive.
The measurements below do not have to be precise -- honestly, I don't even measure when I make this anymore. If I end up with extra stuffing at the end, I just put it in the bottom of the baking dish and cook it with the mushrooms -- it is delicious all by itself. This recipe will yield 3 - 4 servings, depending on the size of your mushroom caps.
Stuffed Mushrooms a la France
8 - 10 large gourmet mushrooms
6 Tablespoons bread crumbs (unseasoned)
6 Tablespoons minced yellow onion (I use shallots instead -- I like the milder flavor)
3 Tablespoons minced green onion
4 - 6 Tablespoons half & half or heavy cream (I usually use heavy cream)
8 Tablespoons fresh parsley, minced (I use flat leaf parsley)
1 teaspoon tarragon (I usually substitute fresh or dried thyme, whichever I happen to have. I'm not a big tarragon fan)
3 Tablespoons butter
1 Tablespoon oil (I use olive oil, but you can use any kind of oil you like)
1/2 cup grated parmesan cheese
1/2 cup shredded Swiss cheese (I usually use shredded parmesan cheese, but both are good)
salt and pepper to taste
1. Pre-heat oven to 425 degrees Farenheit
2. Clean mushrooms and remove stems. Mince the stems and reserve. (If there are some small mushrooms in the package, like there usually are, I also clean and mince them up.)
3. Add oil and butter to a non-stick saute pan and saute the yellow onion (or shallots, whichever you use) for 3 - 4 minutes.
4. Add green onion and mushroom stems, season with salt and pepper to taste, and saute for 2 - 3 minutes more, then turn off heat.
5. Add remaining ingredients (except for shredded Swiss cheese) to the onion-mushroom mixture (I just add it all to the saute pan, but you can do this in a bowl if you prefer) and stir well to thoroughly combine. You want the mixture to be moistened, but not dripping extra liquid, so adjust bread crumbs or cream amounts as needed to get the right consistency (like a thick paste).
6. Place the mushroom caps in a baking dish and fill with stuffing (I usually heap it on pretty good, about 1 heaping Tablespoon per mushroom cap). If you have leftover stuffing, just put in in the baking dish around the mushrooms.
7. Top stuffed mushrooms with shredded Swiss cheese and bake at 425 degrees Farenheit for 20 minutes.