In a small nonstick skillet, cook leek in oil over medium heat for 5 minutes or until tender. Add garlic; cook 1 minute longer. Remove from the heat and set aside.
In the same skillet, melt butter over medium-high heat. In a small bowl, whisk the eggs, water, salt and pepper. Pour into skillet (mixture should set immediately at edges). As eggs set, push cooked edges toward the center, letting uncooked portion flow underneath.
When the eggs are set, spoon leek mixture over one side and sprinkle with cheese; fold other side over filling. Slide omelet onto a plate. Yield: 1 serving.