In a large pot or dutch oven, pour in beef stock and simmer over medium heat.
Add bacon to a skillet and fry over medium heat for 5-7 minutes.
Once the bacon fat has rendered, add the onion pieces and continue frying until both ingredients turn golden brown.
Pour the bacon and onion mixture into the dutch oven with beef stock. Add carrots and parsnip.
Add white kiełbasa (uncut, whole links) and continue cooking for 30-40 minutes.
Meanwhile, boil the eggs. Once cooked allow them to cool to room temperature.
Add 1⅓ cups of zakwas spiced Polish rye sourdough starter for a mild Zurek, or up to 2 cups for a more sour tasting soup.
Add dried marjoram and chopped garlic, cook for another 4-5 minutes.
Take the pot off the heat. Remove the sausage with slotted spoon, slice and return to the pot.
Slowly pour whipping cream into the pot. Have a taste and adjust seasoning with salt & pepper.
Serve Zurek soup in large bowls and top with dollop of sour cream, sliced dill pickles, chopped parsley, spoonful of horseradish and sliced hard boiled egg.