In a medium bowl add the Parmesan cheese, bacon, parsley and salt and pepper to taste. I usually don't add any salt because I find the Parmesan cheese and bacon provides enough saltiness, but I do add about 1/2 tsp of black pepper. Stir everything together and set aside.
In a large oven safe skillet, add the olive oil and heat it over medium heat. Add the mushrooms and cook on both sides for about 2 or 3 minutes per side, just until the mushrooms start to brown a bit.
Add about 1 tbsp of the bacon/cheese mixture to each mushroom, you should have enough to fill all the mushrooms.
Place the mushrooms in the oven and bake for 5 minutes or until the cheese has melted.
To make these ahead for a party, do everything up until step 4, and refrigerate until ready for baking. 5 or 10 minutes before serving, place the mushrooms in the oven and roast them for 5 minutes.Please keep in mind that nutritional information is a rough estimate and can vary greatly based on products used.