Place the white bread into a small bowl submerged in room temperature water. Soak the bread for about 10 to 20 minutes or until it is completely tender. Drain the bread from the water. Discard the water.

Place the herring into a strainer. Drain the liquid and discard the marinated onions. 

Place the onion, apple and soaked bread into a food processor and run the food processor until the ingredients are finely chopped. Add the herring and pulse the mixture about 5 times or until it is finely chopped and incorporated. Make sure not to over-process the mixture. Add 2 hard-boiled eggs and pulse a few more times until the eggs are finely chopped and incorporated well.

Transfer the chopped herring mixture into a mixing bowl. Add the sunflower oil and sugar and stir to combine. Taste for seasoning, adding salt or additional sugar if needed. Set aside.

Separate the yolk and egg white from the remaining hard boiled egg. Chop both separately. Set aside.

To serve, transfer the chopped herring into a serving plate and shape it into a square mound. Garnish by sprinkling 3 vertical stripes of the chopped egg: sprinkle half of the chopped egg whites on the left third of the mound, sprinkle the chopped egg yolk on the center third of the mound and sprinkle the remaining chopped egg whites on the right third of the chopped herring. Serve the chopped herring at room temperature with a slice of rye bread.