Boil 1" of water in a large skillet. Add the asparagus and cook, uncovered just until tender-crisp. Meanwhile, in a medium bowl, whisk together the eggs and water until the whites and the yolks are completely blended. Coat a 10" nonstick skillet with cooking spray. Heat the skillet over medium-high heat until just hot enough to sizzle when a drop of water is added. Pour in the egg mixture. It should set immediately. With an inverted pancake turner, lift the edges as the mixture begins to set to allow the uncooked portion to flow underneath. When the top is set, fill one half of the omelet with the asparagus, mushrooms and cheese. With the pancake turner, fold the omelet in half over the filling, cut in two and serve immediately. Serves 2. Nutrition per serving: 238 calories, 21 g. protein, 5 g. carbohydrate, 15 g. fat, 6 g. saturated fats, 260 mg. sodium, 440 mg. cholesterol, 1 g. fiber.