For the potato soup, finely chop the onion, fry with the bacon in oil.
Soak porcini mushrooms in water, cut and add, pour vegetable soup.
Add peeled and cut potato (leave some for chips), season with marjoram, salt, pepper.
Simmer until potatoes are soft.
Season with sour cream, salt and a dash of vinegar.
Cut very thin slices from the remaining potatoes with a peeler and fry twice.