6 slices bacon, chopped
1 onion, chopped
1 cup finely chopped green bell pepper
4 cups shredded Cheddar cheese
4 slices processed American cheese
1 cup sliced black olives
Preheat oven to 350 degrees F (175 degrees C).
Place bacon in a large, deep skillet. Cook over medium high heat until evenly brown. Remove bacon and place in ovenproof cooler. Drain grease and place bacon in a large skillet. Cook, turning water once, until crisp. Drain grease and reserve in skillet.
Arrange mushrooms on a large baking sheet. Bake, stirring occasionally until nicely brown, 15 minutes. Roast onions in ovenproof cooler for 2 to 3 hours. (Tip: For easier sear, place bacon in skillet with ribs about 1 inch from cheese.
Reduce heat to medium and bake 2 hours. 3 hours is a good time to add some more bacon grease to skillet if desired.)
Beat cream cheese and 1 tablespoon pepper in small bowl until smooth. Mix cream cheese mixture with rolled oats and vanilla. Spread over mushrooms.
Preheat oven to 400 degrees F (200 degrees C).
Bake 20 minutes. Brush mushroom with beaten egg. Bake 10 minutes longer or until fork inserted in center comes out clean. Slice mushrooms with knife and scoop out flesh; discard.
Meanwhile, in a medium skillet over medium heat, brown cheese on one side and processor on the other. Fry mushrooms for 5 minutes. Remove mushrooms from skillet. Stir together cream cheese and chili sauce. Cover skillet and cook 1-over-medium heat, stirring occasionally, until mushroom is no longer pink when centers of cooked mushrooms are seen.
Serve cream cheese mixture over mushrooms. Top with sliced mushrooms and cheeses.