Assemble and attach the KitchenAid® Rotor Slicer/Shredder attachment to the KitchenAid® Stand Mixer. Use the fine shredder cone (No. 1), turn to Speed 4 and shred cheese and onion, keeping each separate. Exchange fine shredder cone for thick slicer cone (No. 3). Turn to Speed 4 and slice mushrooms. Place half of shredded cheese in Baked Pastry Shell. Arrange sliced mushrooms on top of cheese. Arrange onion on top of mushrooms.
Place eggs in KitchenAid® Stand Mixer bowl. Attach bowl and flat beater to mixer. Turn to Speed 4 and beat 3 minutes. Add cream, salt, parsley and hot pepper sauce. Turn to Speed 4 and beat 1 minute. Pour mixture into shell.
Top with remaining cheese and sprinkle with bacon. Bake at 350°F for 30 minutes. Knife inserted in center will come out clean when done. Serve immediately.