Butter a 9 x 13 inch baking dish and line with 8 slices of bread. Sprinkle with cheese, ham, and broccoli. Put 8 slices of bread on top of that mixture. Beat eggs, mustard, salt, and milk together. Pour over bread and cover with foil.
Refrigerate overnight. Mix together corn flakes and melted margarine. Place on top of bread mixture. Bake uncovered at 350°F for 1 hour.