May use all lettuce, if desired.
Cook bacon until crisp, saving the drippings. Beat egg slightly, add 2 tablespoons bacon drippings and remaining ingredients up to sour cream. Mix well. Microwave for 2 to 2 1/2 minutes or until thickened.
Toss together lettuce, spinach, green onions, and crumbled bacon. Just before serving, pour dressing over and toss until well coated. Serve immediately.