Preheat oven to 350degrees. In a small skillet, saute water chestnuts, onion and mushrooms in 2 tablespoons butter 4-5 minutes or until crisp-tender; set aside., In large skillet, melt remaining butter; stir in flour until smooth. Stir in milk, broth, soy sauce, pepper sauce and salt. Bring to a boil; cook and stir 2 minutes or until thickened. Remove from heat; stir in green beans and cheese., Spoon half of the bean mixture into a greased 1-1/2-qt. baking dish. Layer with water chestnut mixture and remaining bean mixture., Bake, uncovered, 45 minutes. Top with French-fried onions. Bake 5 minutes or until heated through.