Soak dried porcini in 125 ml of lukewarm water for about 10 minutes. In the meantime peel and finely dice the shallots. Clean and wash spring onions and cut into slanted rings.
Clean the mushrooms and porcini mushrooms. For larger porcini remove the sponge. If necessary, peel the mushroom feet thinly. Cut porcini and mushrooms into fine slices. Squeeze the soaked porcini well and dice finely.
Save the soaking water. Heat the fat in a pot and sauté the shallots and spring onions with the soaked porcini mushrooms in it. Add the mushrooms and porcini and fry. Dust with flour, sauté until golden yellow and deglaze with vegetable stock and porcini mushroom stock.
Add cream and simmer for 10-15 minutes. Season with salt and pepper. Fill soup into bowls. Serve garnished with chervil as desired.