Soak porcini mushrooms in 1/2 l l lukewarm water for about 20 minutes. Clean, wash and halve or quarter the mushrooms. Peel and finely dice onions
Drain the porcini and collect the soaking water. Chop porcini. Sauté onions in hot oil. Fry mushrooms vigorously, add porcini briefly. Dust with flour and sweat everything. Stir in approx. 1 l water, soaking water, cream and stock, bring to the boil. Then simmer covered for about 20 minutes. Wash the marjoram and chop finely, except for something to garnish. Add to the soup and season to taste
Grate cheese finely and mix with sour cream and egg yolk. Toast bread until golden. Spread with cheese cream and sprinkle with cayenne pepper. Bake on a baking tray lined with baking paper under the hot grill or in the oven at high heat for 3-4 minutes
Arrange the soup and garnish with the rest of the marjoram. Cut the cheese toast into strips and serve with it