Chop the mushrooms stems well.

Heat the butter in a sauté pan, then add the shallots in oil. Let the shallots cook until they are translucent, then add the chopped mushrooms stems. When the stems have softened a bit, add the sherry, and cook the mushrooms down until they are pretty soft.

Add the frozen spinach right into the pan, and stir it in with the mushrooms. It will cook nicely without getting mushy. When the spinach is hot, remove all in the pan to a bowl.

In a separate pan, cook the bacon until crisp but not burned. Chop the bacon finely.

Add the bacon to the mushroom mixture.

Mix all together.

Have the mushrooms on a sheet pan or other oven proof dish.

Using a small spoon, stuff the mushrooms with the stuffing.

Refrigerate for about a half an hour or until ready to cook.

Heat the broiler, and put a bit more Parmesan cheese on top of each mushroom.

Place in the broiler and broil until the cheese has melted and slightly browned.

Serve hot.