Pour the boiling water over the dried porcini mushrooms and set aside for 20 minutes.
Meanwhile get the vegetables ready by peeling and grating 1 beetroot, removing the core and slicing the cabbage, grating the carrots, peeling and cutting the potatoes into chunks, chopping the onion.
Remove the re-hydrated mushrooms from the liquid and chop them. Reserve the liquid to use in soup.
Add the vegetable stock, chopped mushrooms, the bay leaves and the reserved liquid to a large soup pot and bring to simmer. Once it’s simmering add the beets, potatoes, beans, tomato paste and cabbage and cook for 20 minutes.
In the last 10 minutes of the cooking time, sauté the chopped onion and carrots in the butter and oil over low heat until the onions are slightly brown, then add the minced garlic and sauté for 30 seconds longer. Add to the soup and cook for 5 minutes longer. Then add the fresh lemon juice to the soup and salt to taste.
Serve with fresh herbs and sour cream.