In a large skillet, cook bacon until crisp. Remove bacon to paper towel to drain; discard all but 1/4 cup drippings. In the same skillet, add the beef, mushrooms, flour and pepper to the drippings; cook until thoroughly combined. Gradually add milk; cook and stir until thickened. Stir in bacon; set aside., In a large bowl, whisk eggs, evaporated milk and salt. In another large skillet, heat butter until hot. Add egg mixture; cook and stir over medium heat until eggs are completely set., Place half of the eggs in a greased 13x9-in. baking dish; pour half the sauce over the eggs. Repeat layers. Cover and bake at 350degrees for 55-65 minutes or until a knife inserted in the center comes out clean. Let stand 5 minutes before serving.