Step 1

Boil kielbasa and 8 cups water in a large stock pot.

Step 2

Reduce heat to medium-low; cook to flavor broth, about 25 minutes.

Step 3

Pour liquid and kielbasa into a bowl; reserve.

Step 4

Return stockpot to medium heat. Add butter, garlic, leeks, and onion; cook until soft, about 10 minutes.

Step 5

Add reserved liquid, potatoes, marjoram, and bay leaf; boil. Reduce heat to medium-low; cook until potatoes are tender, about 30 minutes.

Step 6

Discard marjoram and bay leaf; purée soup with an immersion blender or regular blender by working in batches.

Step 7

Return soup to pot; bring to a simmer.

Step 8

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 9

Cut kielbasa into 1⁄2″-thick slices; add to soup along with horseradish, salt, and pepper.

Step 10

Garnish with dill, parsley, and eggs.