Wash the potatoes and cook in plenty of boiling water for about 20 minutes. Cut bacon into strips and leave bacon in a pan without adding fat for about 6 minutes until crispy. Peel onions, dice finely and after about 4 minutes add half of the onions to the bacon.
Rinse potatoes under cold water, drain and peel while still hot.
Wash the chives, shake dry, cut into fine rolls. Whisk 2 tbsp. oil, stock, 6 tbsp. vinegar and chives. Season with sugar, salt and pepper. Cut potatoes into slices and toss in the marinade.
Add the bacon and onions and warm the potato salad over a low heat, turning gently and lukewarm. Peel cucumber, cut into thin slices and fold into the potato salad.
Wash the pollock and season with salt and pepper. Heat 1 tablespoon of oil in a frying pan and briefly sauté the remaining onion cubes until translucent. Place the pollack on top and cook in the closed pan for about 4 minutes.
Cut the salmon into fine cubes. Coarsely chop the pollack. Separate egg. Mix fish, egg white, flour and 2 tablespoons breadcrumbs loosely. Shape into approx. 8 meatballs. Press carefully into shape. Turn into 4 tbsp. breadcrumbs.
Place the egg yolks, 4 tablespoons of vinegar, mustard, honey, 1/4 teaspoon salt and 100 ml oil in a tall, slender mixing bowl. Stir with a hand blender to make mayonnaise. Heat 4 tablespoons of oil in a large frying pan and fry the meatballs for approx. 8 minutes, turning them gently.