Serves 6 to 8
We prefer the flavor and texture of Pepperidge Farm Hearty White Bread, although any firm white sandwich bread will do.
| 3 | tablespoons unsalted butter , softened, plus extra for greasing the dish |
| 10 | slices high-quality white sandwich bread (see note above) |
| 12 | ounces cheddar cheese , shredded (3 cups) |
| 8 | large eggs |
| 3 | cups whole milk |
| 1 | onion , grated |
| 1 | teaspoon table salt |
| 1 | teaspoon ground black pepper |
| 1 | teaspoon dry mustard |
| 1/2 | teaspoon Tabasco sauce |
1. Grease the bottom and sides of a 9 by 13-inch baking dish (or casserole dish of similar size) with butter. Spread the remaining 3 tablespoons butter over one side of each slice of bread, then cut the bread into 1-inch pieces. Scatter half of the bread evenly into the prepared dish and sprinkle with half of the cheddar. Repeat with the remaining bread and cheddar. Whisk together the eggs, milk, onion, salt, pepper, mustard, and Tabasco and pour evenly over the bread. Press lightly on the bread to submerge. Cover tightly with plastic wrap and refrigerate for at least 8 hours.
2. Adjust an oven rack to the middle position and heat the oven to 350 degrees. Remove the dish from the refrigerator and uncover. Bake until puffed and golden brown, about 1 hour. Serve immediately.
To Make Ahead
The 24-Hour Omelet and any of its variations can be made and held in the refrigerator, wrapped tightly with plastic wrap, for up to 36 hours before baking.