2 lb. smoked kielbasa
2 tbsp. unsalted butter
4 cloves garlic, finely chopped
2 leeks, trimmed, sliced
1 small yellow onion, sliced
2 medium russet potatoes, peeled and cut into 1? cubes
2 sprigs marjoram
1 bay leaf
1 1?2 cups sour cream
1?4 cup flour
1?4 cup freshly grated horseradish
Kosher salt and freshly ground black pepper, to taste
1?4 cup roughly chopped dill
2 tbsp. chopped parsley
4 boiled eggs, cut into wedges (See How to Hard Boil Eggs)
Step 1: Boil kielbasa and 8 cups water in a 6-qt. saucepan. Reduce heat to medium-low; cook to flavor broth, about 25 minutes. Pour liquid and kielbasa into a bowl; reserve.
Step 2: Return saucepan to medium heat.
Step 3: Add butter, garlic, leeks, and onion; cook until soft, about 10 minutes.
Step 4: Add reserved liquid, potatoes, marjoram, and bay leaf; boil. Reduce heat to medium-low; cook until potatoes are tender, about 30 minutes.
Step 5: Discard marjoram and bay leaf; purée soup in a blender.
Step 6: Return soup to pot; bring to a simmer.
Step 7: Meanwhile, whisk sour cream and flour in a bowl, add 1?2 cup soup, and whisk until smooth. Pour mixture into soup; cook, stirring, until thickened, about 5 minutes.
Step 8: Cut kielbasa into 1?2?-thick slices; add to soup along with horseradish, salt, and pepper.
Step 9: Garnish with dill, parsley, and eggs.