1. Microwave onion and chopped mushroom for 2 minutes on high.
2. Stir and cook a bit longer.
3. While hot, mix in cream cheese.
4. Add bacon.
5. Spoon into mushroom caps.
6. Sprinkle freshly grated parmesan cheese on top.
7. Cover with foil.
8. Bake 20-30 minutes at 350 degrees.