Steps
1. Heat a non-stick pan over medium heat and melt half the butter. Toast the bread slices in the pan until golden and crispy on both sides. Remove and set aside.
2. Wipe the pan clean, add the remaining butter, and crack in the egg. Fry until the white is set but yolk is still runny or cooked to your preference. Season with salt and pepper.
3. Spread mayonnaise on one side of each toasted bread slice.
4. On one slice, place the lettuce leaf on the mayo side. This acts as a moisture barrier to keep the bread crisp.
5. Place the fried egg on top of the lettuce.
6. Cover with the second slice of bread, mayo side down.
7. Press gently and serve immediately, or wrap in parchment paper to maintain crispness if storing briefly.