I discovered this delicious eggy bread (french toast)fr and bacon sandwich recipe in the pages of The Sherlock Holmes Cookbook by Sean Wright.
Sliced bread;
Butter;
2 Eggs, well beaten;
Milk, 1 1/2 cups;
Salt, 1/4 teaspoon;
Bacon drippings, 1-2 tablespoons;
Onion, a few slices;
3 or 4 rashers of bacon, cut in half or diced.
Spread the bread with softened butter and set aside.
Saute the sliced onions in the bacon fat in the pan until lightly browned. Remove from the pan and pat dry.
Spread half the slices of bread with the fried onion.
Lay the bacon strips on the onions and top with the remaining slices of bread.
Combine the eggs, milk, and salt, mixing slightly.
Dip the sandwich in the egg mixture, carefully placing it back in the heated skillet. Add more bacon drippings if necessary and fry quickly on each side.
These sandwiches may also be prepared in a waffle iron or sandwich toaster, using a richer egg mixture (3 well-beaten eggs, 1/4 cup of milk, 1/2 teaspoon salt, and 1 tablespoon of melted butter).
There are many variations of this sandwich, the fillings including crabmeat, cheese, ham liver, chicken, fish and so on.
https://thejollyhog.com/2021/02/25/ultimate-bacon-eggy-bread/