COAT 12-oz. microwave-safe coffee mug with cooking spray. ADD egg, water, broccoli and mushrooms; BEAT until blended. MICROWAVE on HIGH 30 seconds; STIR. MICROWAVE until egg is almost set, 30 to 45 seconds longer.
SEASON with salt and pepper if desired. TOP with cheese and walnuts. SERVE immediately.
Substitute spinach for broccoli and use cheddar cheese and cooked, chopped bacon for a savory taste.
Microwave ovens vary. Cooking times may need to be adjusted.
This recipe is an excellent source of protein and choline, and a good source of vitamin A and folate.