Place the mushrooms in a 2-cup (or 4-cup) glass measure and cover with vented plastic wrap.
Microwave on high for 2 to 3 minutes, or until the mushrooms are wilted.
Drain off any liquid.
In a medium bowl, whisk together the eggs, water, basil and pepper.
In a medium non-stick frying pan over medium heat, melt the margarine.
Swirl the pan to coat the bottom.
Add the egg mixture.
As the eggs begin to set, pull the outer edges toward the center with a fork or spatula; allow uncooked portions to run underneath.
Continue until the eggs are just barely set.
Sprinkle with the mushrooms and Parmesan.
Fold the omelet in half.
Transfer to serving plate.