When you’re pressed for time or simply desire lighter fare, this tasty omelette takes only a few minutes to make, yet provides essential nutrients.
In small bowl, with a fork, lightly beat together eggs, water and tarragon (if using). Season with salt and pepper to taste.
In 8-inch (20 cm) nonstick skillet, melt butter over medium-high heat. Add mushrooms and onion and cook until tender, about 2 minutes. Remove vegetables to a plate.
Add egg mixture to skillet. As mixture sets at edges, use spatula to gently push cooked portions to the centre, tilting and rotating pan to let uncooked egg flow underneath. Just before completely set, spread evenly in pan.
Spoon filling over half the omelette; fold uncovered side over filling and lift onto serving plate.
Garnish with fresh tarragon, if using.