Wash the tomatoes, dry and cut into thin slices. Rub the bread slices on all sides with a clove of garlic. Wash the egg, separate the white from the yolk. Using a mixer, beat the egg whites until stiff foam forms. Wash the greens for serving, dry and chop. Prepare a baking tray. Turn the oven on 180 degrees.
Prepare the filling. Place the yolk in a separate container and grind until light yellow. Then season with mustard and mayonnaise and mix thoroughly. Without ceasing to stir, carefully fold the prepared whites into the mixture.
Prepare the dish. Place tomato slices on bread slices and distribute sardines on top. Place the semi-finished product on a baking sheet and carefully pour the prepared egg mixture over each toast. Then place the pan in the oven for 15 minutes.
Serve toast with canned sardines as a light snack. Use chopped herbs as a decoration - sprinkle them on the finished dish.