1/3 cup (1 ounce) dried porcini
2 large leeks
3 or 4 small russet potatoes, peeled
1 1/4 pounds beets, peeled
3 celery ribs
finely chopped parsley or dill
3 bay leaves
7 garlic cloves, chopped
sea salt and freshly ground pepper
1 large onion
1 rutabaga, about 1/2 pound
2 tbsp butter
3 cups shredded green cabbage
1 cup fresh or canned diced tomatoes (in puree or water)
1 tbsp sugar
3 tbsp white or red wine vinegar
1/2 cup sour cream mixed with 1 tbsp prepared horseradish
Cover the mushrooms with 2 cups warm water and set them aside while you make a vegetable stock. Wash all the soup vegetables thoroughly since you’ll be using the trimmings. These include 4 inches of leeks past the white part of their roots, if available; potato peels; beet stems and peels; celery tips; carrot ends; and parsley stems. Put the trimmings in a pot with 2 bay leaves, 4 garlic cloves, and 2 teaspoons salt. Cover with 10 cups water and bring to a boil. Lower the heat and simmer while you chop the vegetables for the soup.
Finely chop the white parts of the leeks. Finely dice the onion. Chop the celery into 1/2-inch pieces. Dice the carrot into 1/4-inch piece. Peel the rutabaga and dice into 1/2-inch pieces. Dice the peeled potatoes. Cut the peeled beets into julienne strips.
Melt the butter in a large Dutch oven. Add the leeks, onion, celery, carrot, rutabaga, potatoes, cabbage and remaining garlic. Toss with 1 tablespoon salt, cover, and cook over medium heat until the vegetables have wilted, about 20 minutes. Add the beets, tomatoes, remaining bay leaf, and sugar. Chop the soaked mushrooms and add them, along with their soaking liquid, to the pot. Strain the stock, then add it (or 2 quarts water) and simmer until the beets are tender, about 25 minutes. Taste for salt and season with pepper. Stir in the vinegar.
Serve hot or cold, with a spoonful of sour cream and horseradish in each bowl and a scattering of fresh green parsley or dill. SERVES 8 TO 10