Brush the sandwich toaster with a little sunflower oil and preheat to its highest setting.
Pour the beaten egg onto a large dinner plate and soak the bread in the egg, turning it over until all the egg has been absorbed.
When the toaster is ready, place one slice of eggy bread on the bottom plate. Top with the bacon and spread over the ketchup (if using). Finish the sandwich by placing the second slice of eggy bread on top. Slowly close the lid of the toaster and cook for 3-4 minutes until crisp and golden.