1 loaf of uncut white bread (preferably pullman), about 10 inches long
6 tablespoons unsalted butter
Kosher salt and freshly ground black pepper
8 slices of American cheese
8 slices of bacon, sliced into 1/2-inch pieces
1/3 cup whole milk
12 large eggs
Hot sauce, for serving
Place an oven rack in the middle of the oven and preheat to 375 degrees F.
Remove 1/4 inch of the crust from the ends of the loaf, then cut the loaf crosswise into 4 pieces. Use a fork to score a cut end and gently dig a square hole into each piece of bread to make a box and leave a 1/2-inch layer of bread around the walls and floor. Save the removed crumbs for another use.
Microwelle the butter and a large pinch of salt in a small microwave-safe bowl until melted, about 1 minute. Clean the bread boxes with the melted butter. Place 1 piece of cheese on the bottom of each bread box. Place the bags open on a baking tray and bake until the cheese melts and the inside of the bread is slightly browned and crisp in parts, about 10 minutes.
Meanwhile, heat a large non-stick pan over medium heat and add the bacon. Cook, stir occasionally, until the bacon is crisp, 12 to 15 minutes. Use a slotted spoon to put the bacon on a plate with a paper towel. Reserve the fat in the pan and adjust the heat to low. Beat the milk and the eggs with a big pinch of salt and pepper and add the pan. Continue to stir the eggs, scrape the sides of the pan as needed until small quark form and the eggs are just set, 6 to 8 minutes.
Divide the hot eggs between the 4 boxes and above with the remaining cheese. Return to the oven and bake until the cheese melts, about 5 minutes. Top with the crispy bacon and served hot with hot sauce and additionally salt and pepper.