- 1-ounce (30 g) dried porcini mushrooms
- 2 tablespoons vegetable oil
- 1/2 pound white mushrooms, trimmed, wiped clean, and sliced 1/4 inch thick
- 1 large onion, cut into 1/4-inch dice
- 10 small or 7 to 8 medium beets, with greens, peeled, quartered, and cut across into 1/4-inch slices
- 2 medium carrots, peeled and cut across into 1/4-inch rounds
- 1 medium parsnip, peeled and cut across into 1/4-inch rounds
- 1 very small or 1/2 large celery root (about 3/4 pound), peeled and cut into 1/2 inch cubes
- 1 1/2 pounds mashing potatoes, peeled and cut into 1/2-inch cubes
- 1/2 small white cabbage (about 3/4 pound), cored and shredded
- 3 large cloves garlic, smashed, peeled, and very finely chopped
- 3 tablespoons tomato paste
- 1 medium bunch dill, fronds only, coarsely chopped
- 1/4 cup sugar
- 1/2 cup cider vinegar
- 2 tablespoons kosher salt
- Freshly ground black pepper, to taste
- Coarsely chopped dill
- Sour cream
- Boiled potatoes, optional
Soak the dried mushrooms in 1 cup hot water for 15 minutes. Drain, reserving the liquid, and squeeze out the excess liquid. Strain all the soaking liquid through a fine-mesh sieve. Reserve the liquid (there should be 1 cup) and the mushrooms separately.
In a tall narrow stockpot, heat the oil over medium heat. Stir in the fresh mushrooms and cook, stirring occasionally, for 4 minutes. Stir in the onion and cook, stirring occasionally, for 8 minutes.
Add the beets, carrots, parsnip, celery root, 8 cups water, and the mushroom soaking liquid. bring to a boil. Lower the heat and simmer for 5 minutes. Stir in the potatoes, cabbage, garlic, and, if using, the beet greens. Dissolve the tomato paste in 1/2 cup of the liquid and stir back into soup. Return to a boil. Lower the heat and simmer for 5 minutes. Stir in the reconstituted mushrooms and simmer for 5 minutes, or until all the vegetables are tender.
Remove from the heat. Stir in the dill, sugar, vinegar, salt and pepper.
Pass bowls of chopped dill and sour cream at the table.