Cut the cold, peeled potatoes into slices. Dice the onion and pickles. Finely slice the radishes. Add a little salt and pepper and stir carefully.
The dressing:
Mix yogurt, buttermilk, oil, vinegar, herbs, pressed garlic, sugar, salt and pepper well together. Chop the very hard-boiled eggs and fold into the dressing.
Pour everything over the potatoes, radishes, pickles. Mix again and let it steep a little. If necessary, add seasoning, as the potatoes soak up a lot of seasoning.
Of course you can change the amount of the individual ingredients.
A nice, tasty and faster alternative is this salad with pasta instead of jacket potatoes.