My all time favorite appetizer! They're pretty easy to make. I've never made them ahead, but I suppose you could stuff them ahead of time and just throw them in the oven at the last minute.

French Stuffed Mushrooms

1 package mushrooms with stems removed
3 Tbs minced parsley
1/4 c butter
3 Tbs cream
1/4 c bread crumbs
3 Tbs shallots, minced
1/4 c dry red wine
1/2 tsp tarragon
1 Tbs olive oil
1/4 c grated Swiss cheese, plus a bit extra for topping

Brush mushrooms with melted butter, reserving about 2 Tbs for topping. Saute shallots in oil. When soft, add wine and boil to a glaze. Remove from heat and add bread crumbs, cheese, parsley and tarragon. Blend in enough cream to moisten mixture until it will hold it's shape. Fill mushroom caps. Drizzle remaining butter over mushrooms and top with a pinch of cheese. Bake at 375 degrees for 15 to 20 minutes.