For the potato salad with dill dressing, boil the potatoes in enough salted water (about 30 minutes). Peel the potatoes, cut into slices and let cool in a bowl.
Mix in the onion. In a narrow tall container, add the yolks, mustard, lemon juice and salt and pepper.
Then put in the blender (not yet turned on). Now pour in the oil. Turn on the blender and slowly pull it up.
Stir the dill and sour cream into the resulting sauce, season to taste and mix with the potatoes.
Serve the potato salad with dill dressing garnished with fresh dill sprigs.