Boil the potatoes.Cook the potatoes in cold salted water for 15–20 minutes until just tender, then drain and cool.
Prepare the cabbage.Shred the cabbage, add 1 teaspoon of salt, massage it thoroughly and leave it for 10–15 minutes.
Dress the cabbage.Add the apple cider vinegar, sugar and 2 tablespoons of olive oil, then mix thoroughly.
Cook the onion.Cook the half-ringed onion with 1 tablespoon of olive oil and 1 teaspoon of sugar for 5–7 minutes over medium heat.
Prepare the cucumber.Cut approximately 150 g of pickled cucumbers into rings and drain away any excess liquid.
Blend the dressing.Blend the olive oil, milk, salt, black pepper and Dijon mustard until creamy and well combined.
Cut the potatoes.Coarsely cut the cooled potatoes into irregular pieces and place them in a large bowl.
Add the dressing.Pour the creamy dressing over the potatoes and gently fold them together with a large spoon.
Add the vegetables.Fold in the cabbage, softened onion and pickled cucumber without crushing the potatoes.
Rest and serve.Allow the finished salad to rest for 10–15 minutes before serving slightly cool or at room temperature.