Cook bacon; drain, reserving 1/4 cup drippings. Combine flour and reserved drippings over low heat, blending unitl smooth. Gradually add milk; cook until smooth and thickened, stirring constantly. Add Cheddar cheese and dry mustard, stirring until cheese melts.
Place 3 slices bacon on each slice of bread, and top with 2 slices of chicken. Place in a 13x9x2" baking pan; cover with cheese sauce, and sprinkle with Parmesan cheese. Bake at 350 degrees for 10 minutes or until bubbly.
