Boil the eggs for 10 minutes, then remove from the water and run under cold water - this prevents them from continuing to cook and from the yolks from turning grey. When they are cool, peel them and add them to a small bowl.
Add the mayonnaise, salt and pepper and carefully mash the eggs with the back of a fork. Season with a little salt and pepper.
Fold together until all is combined.
Spread egg mix onto one slice of the bread, top with lettuce, tomato, Spanish onion and cress.
