1. Preheat oven to 400°.
2. Combine stock, 1 cup onion, half of mushrooms, and garlic in a saucepan; bring to a boil. Cover, reduce heat, and simmer 10 minutes or until mushrooms are tender. Place mixture in a blender. Remove center piece of blender lid (to allow steam to escape); secure blender lid on blender. Place a clean towel over opening in blender lid (to avoid splatters); blend until smooth. Stir in sour cream, pepper, salt, and 2 ounces cheese; blend until smooth.
3. Cook bacon in a large cast-iron skillet over medium heat until crisp. Remove bacon from pan; crumble. Add half of potatoes to drippings in pan; cover and cook 4 minutes on each side or until browned. Remove potatoes from pan. Repeat procedure with remaining potatoes and 2 teaspoons oil. Remove from pan.
4. Add remaining 1 teaspoon oil to pan; swirl to coat. Add remaining 1 cup onion and remaining half of mushrooms to pan; cook 6 minutes or until tender, stirring occasionally. Return potatoes to pan; add eggs, stirring well to combine. Pour sour cream mixture evenly over potato mixture. Sprinkle with bacon, the remaining 2 ounces cheese, chips, and parsley. Bake at 400° for 10 minutes or until cheese melts. Turn broiler on (do not remove pan from oven); broil 1 1/2 minutes or until lightly browned.