Cook the potatoes for 20-22 minutes. Remove the cooking water and let the potatoes rest in the open pot for a few minutes, allowing the steam to escape. Peel them while still hot, let them cool off and then slice them. Cut the onion into thin rings and dice the cucumber, not very thinly. Snip the dill and set some of it aside for decoration.
In a bowl, mix the sour cream with the snipped dill, the sea salt and the poppy seed oil.
Add the potato, the onion and the cucumber to the flavored sour cream and mix them together thoroughly. When it is done, pour it into a nice serving dish. Garnish it with the rest of the dill.