Preheat oven to 400 degrees.
Place bacon in a large skillet and cook until browned and crispy. Transfer to a paper towel to drain. Crumble bacon.
Heat olive oil in a large skillet set over medium heat. Add mushrooms and black pepper and cook, stirring occasionally, about 3 minutes.
Add chopped sage and cook until mushrooms are tender, an additional 3 to 4 minutes. Add crumbled bacon. Taste and season with salt, to taste.
Coat four 6-ounce ramekins with nonstick cooking spray or grease with butter. Divide the mushroom mixture between the ramekins.
In a large bowl, whisk together eggs, egg whites and water. Divide the mixture between the ramekins, pouring over the mushroom mixture.
Place the ramekins on a baking sheet and place in the oven. Cook until the eggs are set, about 20 minutes. A few minutes before the cooking is done, sprinkle the eggs with Parmesan and place back into the oven.
Remove from the oven, transfer the ramekins to plates (make sure they don't slide around) and serve immediately.
Make-ahead: The night before, you can make the mushroom, sage and bacon mixture and prepare the egg mixture. Place the mushroom mixture in the prepared ramekins. Cover and chill the ramekins and the egg mixture. In the morning, pour the egg mixture over the mushrooms and bake as directed.