Boil 750 ml salted water. Remove the pot from the stove, add milk, stir in the puree powder with a wooden spoon. In the meantime heat 1 tablespoon of oil in a pan. Beat the eggs, slide them into the hot oil and fry for about 5 minutes.
Season with a little salt. Cut the cucumbers into slices. Arrange rollmops, cucumber, corned beef, puree and eggs on plates.