Place bacon in a large, deep skillet. Cook over medium-high heat until evenly brown.
Drain, crumble, and set aside. Reserve 1/4 cup of bacon drippings in the skillet.
Place green beans and water in a medium saucepan, and bring to a boil. Reduce heat, cover, and simmer 6 minutes, or until tender but crisp; drain.
Place mushrooms and onion into the skillet with the reserved bacon drippings. Cook and stir over medium-high heat for 10 minutes; drain. Reserving 2 tablespoons for topping, mix the crumbled bacon into the skillet. Stir in the green beans. Season with pepper, and transfer to a 2 quart baking dish.
Melt the cheese sauce in the microwave, and pour over the green bean mixture.
