Prepare a bowl of very cold water. In a saucepan, bring water to a boil. Place your egg in a tablespoon and gently lower it into the boiling water. Cook for 7 minutes if the egg is from the fridge, otherwise 6 minutes and 30 seconds if it's not.

Remove the egg from the water and immediately plunge it into the cold water. Slightly crack the shell in the water.

Wait for 10 minutes in the water before peeling.

Cut your egg in half and remove the yolk.

Finely chop the whites with a knife.

Put the yolks in a bowl and mash them with a fork. Add the sugar, salt, pepper, mayonnaise, and milk.

Mix well until you have an even mixture.

Spread plastic wrap on your work surface. Place the slices of bread on top and spread butter on them. Next, place your egg mixture on one slice of bread, leaving a 1 cm margin on the sides. Don't hesitate to make a small mound.

Place the other slice of bread on top, then wrap it tightly with plastic wrap and refrigerate for 20 minutes.

Remove the plastic wrap, cut off the crusts with a knife, and cut in half. It's ready!