Make ahead: Clean and peel the vegetables (1 large carrot, 1 medium parsley root, 3 and ½ ounces celeriac root, 4 medium potatoes). Cut them into ½-inch cubes. Peel and mince 3 cloves garlic. Peel and finely chop 3 medium onions. Grind ½ teaspoon caraway seeds coarsely either in a grinder or by hand in a mortar.
Soak 1 handful dried mushrooms in 1 ¼ cups water, bring to a boil, and gently simmer for about 10 minutes. Reserve the mushroom stock for later.
Heat a Dutch oven or a thick-bottomed soup pot over medium heat and melt in ¾ stick unsalted butter. Add the root vegetables (carrot, parsley root, celery—not the onion yet).
Fry the vegetables until lightly golden (5-8 minutes), stirring occasionally. Add the onion and cook for 5 minutes while stirring.
Reduce the heat to one-third and start making the roux. Add ⅓ cup all-purpose flour to the vegetables and fry for about a minute, until the veggies are coated with flour and lightly golden. Stir frequently to prevent the flour from scorching. Add crushed caraway seeds and ¼ teaspoon ground black pepper Stir well.
Add about a cup of lukewarm water or vegetable broth and whisk to prevent lumps. Add the remaining liquid and stir. Salt to taste, turn up the heat, cover and bring to a boil.
Once the soup starts to boil, add the cubed potatoes and boil gently for 10 minutes. Then add the chopped garlic, soaked mushrooms and about 1 cup of reserved mushroom stock. Reduce heat and let cook covered for about 5-7 minutes, or until potatoes are tender.
The last step is to add the 1 Tablespoon dried marjoram. Rub the marjoram with your fingers before adding it to release its essential oils. Cook for another 1 minute, then remove the bramboracka soup from the heat.
Taste and season with salt and pepper if necessary. Stir in 1 Tablespoon fresh parsley greens, chopped.