In a large mixing bowl, whisk together eggs, egg whites, salt and pepper until slightly frothy, about 30 seconds. Set aside.Heat oil in a skillet over medium heat. When pan is hot, add leeks and mushrooms; sauté for 8 to 10 minutes. Ass garlic; sauté for another minute.Pour egg mixture over leeks and mushrooms. Gently lift the edges of the omelet with a spatula to let uncooked egg run underneath. Continue to cook until eggs are set, about 4 to 5 minutes. Run a spatula around the edges of the omelet and under it to loosen it from the pan. Sprinkle half of the omelet with cheese, and then gently fold in half. Continue to cook for 3 to 4 minutes, or until eggs are firm.Remove from heat and serve immediately.Serves 2.Nutrition: Per serving: 230 cal, 17 g pro, 12 g total fat (2 g saturated fat), 13 g carb, 2 g fibre, 170 mg chol, 310 mg sodium