Soak dried porcini for about 1 hour in 200 ml cold water. Clean and wash the porcini and, except for some for garnishing, cut them into large pieces. Peel and finely chop the onion. Peel, wash and finely dice the potatoes. Heat butter in a pot.
Sauté the potatoes in it. Add onion and porcini mushrooms and sauté briefly. Deglaze with broth. Add mushrooms in the soaking water. Bring to the boil and simmer for about 15 minutes. Puree soup and pour through a fine sieve. Refine with cream and season to taste with lemon juice, salt and pepper. Bring to the boil again. Cut mushrooms aside into fine slices. Heat the oil in a pan and fry the slices for 1-2 minutes while turning.
Refine with cream and season to taste with lemon juice, salt and pepper. Bring to the boil again. Cut mushrooms aside into fine slices. Heat the oil in a pan and fry the slices for 1-2 minutes while turning. Take them out and let them drain. Wash the marjoram, dab dry and pluck the leaves from the stalks. Serve the soup and garnish with marjoram and slices of mushrooms
Waiting time approx. 45 minutes