Rich, hearty and all-around delicious, this sourdough soup simmering on your stove will let you know that dinner is covered! Based on a Polish-style Zurek, this sourdough soup is not very traditional as I’ve tinkered with it and made it my own using my sourdough starter to thicken and add flavor to the soup. You can adjust the flavor of the soup to be more sour or less sour depending on your sourdough starter. So, what do you say? Are you willing to try it? My family was pleasantly surprised by the deliciousness of this soup and will be making it often during soup season. It’s the perfect soup to serve in a sourdough bread bowl too!
Important Ingredients in Sourdough Soup
Sourdough Starter: This soup is made with a rye levain. Use some of your sourdough starter to mix up the levain. If you prefer, you can substitute a cup of active sourdough starter OR a cup of sourdough discard for the rye levain in the soup. See recipe notes for details.
Rye Flour: I make a rye levain using rye flour to add to this soup. It is used to thicken the soup and gives a delicious flavor. Any rye flour will work in this recipe (including pumpernickel).
Bacon: I use about 8 oz in this recipe, 1/2 a package.
Polish Kielbasa: Authentic Polish Kielbasa is difficult to find where I live, but this soup is really my own concoction anyway, so feel free to use any type of pork sausage. This is the one I buy. I like using a pre-cooked sausage. If you can’t find it, you can substitute for any favorite pork sausage.
Chicken Stock: This soup needs some type of stock for flavor. I like the flavor of the chicken stock but you can use beef stock or vegetable stock too if you prefer. I’ve also used bouillon cubes mixed with water.
Potatoes: I love the small creamer potatoes for this recipe, but russet potatoes will work too. Chop them so they are bite-sized.
Marjoram: Dried marjoram gives a nice earthy/woodsy flavor to this soup, giving it depth of flavor. Substitute oregano or thyme if you can’t find it and like those flavors.
Bay Leaf: Simmer the soup with a bay leaf and remove it before serving. This enhances the soups flavor.
Sour Cream: I love adding a dollop of sour cream to the top of the bowl of soup when serving. It makes the soup creamy and enhances the mild (or strong–if you make it that way) sour notes.
Mixing Up a Rye Levain
The heart of this soup comes from the rye levain that is used to thicken the soup. In a traditional Polish Zurek, the soup is thickened and flavored with ‘Sour Rye Zakwas’ which takes a few days to make or is easily purchased (in Poland). But this recipe is not at all traditional, so I took my sourdough starter and made a rye levain from it to use as a thickener for the soup.
Make the levain 9-11 hours before you make the soup. Take 10 grams of ripe/bubbly/active sourdough starter. Feed it 100 grams rye flour and 100 grams water. Cover and let sit overnight until doubled in size, bubbly and peaked. If you keep the levain at 78 degrees, this should take about 9-11 hours.
Sauté the Meat
Place a Dutch oven or a medium-sized soup pot over medium-low heat.
- Bacon: Cut up the bacon into small pieces. I like using kitchen scissors. Cook for about 5-7 minutes until crispy. Remove the crispy bacon pieces to a plate lined with paper towel (to soak up the bacon grease).
- Sausage: Leave the bacon grease in the pan. Slice up the sausage into bite-sized pieces and sauté until warmed through and crisped. If your sausage is not pre-cooked, make sure to cook it completely in this step. Transfer the cooked sausage to the same plate as the bacon and set aside while you make the broth.
Soup Broth Base and Potatoes
- Soup Base: Add diced onion and garlic to the bacon grease in the pot. Sauté until softened. Pour the chicken stock into the pot and deglaze, scraping up all the little brown bits from the bottom. Transfer the stock/onion/garlic to a blender and blend the broth until it is smooth. A hand-held immersion blender also works great, or skip this step if you don’t mind little pieces of garlic and onion in your soup. Add the broth back into the pot over medium-low heat.
- Potatoes: Cut potatoes into bite-sized pieces. I like using the small creamer potatoes in this recipe, but russet potatoes work well too. Add the potatoes to the pot along with the marjoram and bay leaf. Simmer the soup until the potatoes are fork tender, about 15-20 minutes.
Mix in Rye Levain
Once the potatoes are cooked through, it’s time to thicken the soup with the rye levain. Add 1/4 cup cool water to the rye levain (all 200 grams of it). Mix until combined and the consistency becomes a little thinner. Working quickly, ladle 1/2 cup of the soup broth into the rye levain and stir together. The soup will be hot, so you want to quickly whisk together the soup with the rye levain mixture until incorporated. Pour this mixture into the soup and stir. The rye starter will add flavor and thicken the soup as it simmers. If the soup is too thick, add a little broth or water until it reaches the desired consistency.
Simmer and Serve Sourdough Soup
Add the bacon and sausage back into the soup. Simmer for a few minutes and serve hot. We love serving the sourdough soup in homemade sourdough bread bowls. Add a dollop of sour cream to the top. I love the extra flavor and creaminess the sour cream brings. This soup is also often served with hard boiled egg and a touch of horseradish. However you choose to serve it, it’s hearty and delicious! Enjoy!
Frequently Asked Questions
How do you store leftover soup?
Leftover soup can be stored in the refrigerator for 3-5 days or frozen for up to a couple of months. Re-heat and thin with a little water or broth to serve.
Does this soup taste very sour?
It depends on how sour your starter or rye levain is. If you use your rye levain when it peaks, it will have a slightly pleasant tang. If you wait longer and use it significantly after peak, it will taste more sour.
Do you get sourdough health benefits from this soup?
Yes! One of the beautiful parts of this soup is the health benefits from the fermentation process. This soup is thickened with a starter instead of a traditional roux (flour and butter). You get all those same health benefits in the soup.
What kind of rye flour should I use? Can I use pumpernickel flour?
Any rye flour will work to make the levain for this soup. Pumpernickel flour is the darkest type of rye flour and will give you the deepest rye flavor in the soup.
Can I use my sourdough starter to thicken something other than soup?
Yes! You can use it to thicken gravies, pasta sauces and even pumpkin pie!
Rye Levain (1:10:10, ready in 9-11 hours up to 24 hours for a more sour flavor)
- 10 grams ripe sourdough starter
- 100 grams water
- 100 grams rye flour
- 8 oz bacon
- 1 lb Polish Kielbasa, pre-cooked see recipe notes
- 4 cloves garlic minced
- 1 medium onion diced
- 6 cups chicken stock beef or vegetable stock also work
- 2 lbs potatoes roughly chopped, I like using the small creamer potatoes
- 1 Tablespoon marjoram see recipe notes
- 1 bay leaf
- 1/2 teaspoon salt to taste
- 1/4 teaspoon pepper
- all of the rye starter see recipe notes
- sour cream as desired to top the soup
- The day or night before making this soup, mix together 10 grams sourdough starter with 100 grams rye flour and 100 grams water. Cover and let sit until at 78 degrees F until fermented (takes about 9-11 hours at this temperature for the starter to peak). This rye levain can be used right when it peaks or after it peaks. For a more sour flavor, put the peaked rye levain in the fridge and use it after a few days.The longer the rye starter sits, the more sour flavor the soup will have. See recipe notes for substituting sourdough starter/discard for the rye levain.
- Place a Dutch oven pot over medium heat. Use kitchen scissors to cut the bacon into small pieces and fry until crispy and brown, stirring occasionally. This usually takes about 5-7 minutes. Remove the crispy bacon to a plate and set aside.
- Cut up pre-cooked Polish Kielbasa into bite-sized pieces. Fry in the bacon fat until crisped and warm, about 3-5 minutes. Set aside.
- Dice an onion and garlic. Add to the pot and cook over medium-low heat in the bacon grease until softened, about 2-3 minutes. If the bacon grease seems used up and the vegetables are sticking, add a tablespoon of butter to the pot. Pour in the chicken stock and scrape all the little brown bits off the bottom of the pan.
- Pour the chicken stock/onion/garlic mixture into a blender and blend until smooth. Transfer the liquid back to the pot.
- Cut potatoes into bite-sized pieces and add to the pot. Add 1 Tablespoon marjoram and 1 bay leaf to the pot. Stir. Let potatoes cook and simmer for about 15-20 minutes until they are fork tender. Stir occasionally. Take a fork and prick a potato. If the fork glides through it and the potato is soft, you are ready to finish up the soup.
- Add 1/4 cup cool water to the rye levain. Mix until combined. Working quickly, ladle 1/2 cup of the soup broth into the rye levain. Quickly whisk together the soup with the sourdough starter until combined. Pour this mixture into the soup and stir. The rye starter will flavor the soup and thicken the soup as it simmers. If the soup is too thick, add a little broth or water until it reaches the desired consistency.
- Add in the reserved cooked meats and stir together. Taste the soup. Add salt and pepper to taste. Serve soup in bowls or sourdough bread bowls with a dollop of sour cream on top. Enjoy!