Peel the potatoes and cook them in salted water as usual. After cooking, let it cool completely and cut into cubes or slices. Wash or peel the cucumber and quarter it lengthways. Remove the seeds, cut the rest into pieces and add to the potatoes.
Peel the onions as well and cut them into not too fine cubes. Wash the dill, shake dry and chop. Add onion and dill to the other ingredients in the bowl along with about 1 1/2 packets of salad dressing mixture, oil (no olive oil, as it has a too dominant taste) and mix well.
Let it stand for about 2 hours and season with salt and pepper and / or the rest of the salad dressing mixture. If there is not enough liquid, a little more water can be added, but the cucumbers usually still pull well.
The whole thing tastes good with jacket potatoes too, of course. If you like, you can leave the peel of the potatoes on, the salad then tastes stronger (earthier).
The salad tastes best if you prepare it a day in advance.