1
Lightly grease 13x9-inch baking pan.
2
In saucepan, melt 2 tablespoons butter. Whisk in flour; cook 1 minute. Gradually stir in milk. Cook, stirring constantly, until thickened. Remove from heat. Stir in cheese, salt and pepper; cool slightly.
3
Meanwhile, in large skillet, melt 1 tablespoon butter. Add mushrooms and Canadian bacon; sauté until golden brown. Add eggs and onions. Cook over medium heat until eggs are soft scrambled.
4
Stir cheese sauce into egg mixture. Pour egg mixture into baking pan.
5
In small bowl, combine cornflakes and 1/4 cup melted butter; sprinkle over egg mixture. Refrigerate overnight.
6
Heat oven to 350ºF. Bake casserole 30 minutes or until heated thoroughly.