Wash mushrooms and carefully remove the stems from the center of the caps. Place the caps into a suitable flat baking pan with hole from the stem up. Fry the bacon until it is crunchy. Chop the stems from the mushrooms very finely with a chopper. In a large bowl mix the chopped stems, 1/2 cup breadcrumbs, and fried bacon (including the bacon grease for flavor). Fill each cap until heaped with the stuffing mixture. Heat in microwave or oven until hot.