In a fry pan, melt butter over med. heat, add mushrooms and onions. Cook until mushrooms are browned (10-15 min.), stirring often. Mix in sherry. Remove from heat,set aside. In a bowl, beat cream cheese and parsley until blended, and then add mushroom mixture. Blend. (If you want the pieces of mushroom, just stir. I like to Cuisinart in, so it's the same consistency as pate.) Refrigerate, and serve with breads or crackers.