Soak the boletus in cold water and set aside. Peel the carrots, celery, onions and garlic, cut into small cubes and set aside. Peel and wash the potatoes and also cut into small cubes.
Heat the oil in a large saucepan and sauté the soup vegetables with the garlic for a few minutes. It should be a bit soft afterwards.
Remove the porcini mushrooms from the soaking water and finely chop them. Do not throw away the soaking water, it is also added to the soup. Now add the mushrooms to the soup vegetables and steam them with them.
After about 5 minutes, add the potato cubes to the vegetables, add the vegetable stock, soaking water and bay leaf. Cook on medium heat for approx. 15-20 minutes until the vegetables are soft. Remove the bay leaf, add the cream and finely puree the soup with the hand blender. Then season with salt, pepper and nutmeg.