- 3 tablespoons butter or margarine, divided
- 1 1/2 tablespoons all-purpose flour
- 1/2 teaspoon salt
- 1 1/4 cups milk
- 1 3/4 cups shredded cheese (such as Cheddar or Swiss), divided
- 1 cup sliced mushrooms
- 1/3 cup finely chopped onion
- 12 eggs
- 6 slices cooked bacon, chopped
- Melt 1 tbsp of the butter in a saucepan. Whisk in flour and salt. Gradually whisk in milk until smooth. Bring mixture to a simmer over medium heat, stirring constantly, until slightly thickened. Remove from heat. Add 1-1/4 cups of the cheese, stirring until melted. Set aside.
- Melt remaining 2 tbsp butter in a large frying pan. Add mushrooms and onion; saute until tender and liquid evaporates.
- Whisk eggs. Add eggs and bacon or ham to mushroom/onion mixture. Cook until eggs are just set but still a little wet. Stir cheese sauce into egg mixture.
- Spoon mixture into a greased 9-inch (23 cm) square baking pan or 2.5 L casserole. Sprinkle remaining 1/2 cup cheese over top. Cover and refrigerate overnight.
- The next morning, uncover and bake in a preheated 350 degrees F (180 degrees C) oven until heated through and cheese is melted, 20 to 25 minutes.