Why You’ll Love This Recipe
- Uses sourdough discard or active starter
- No preservatives or artificial ingredients
- Rich mushroom flavor with natural umami
- Perfect substitute for canned cream soups
- Freezer-friendly and meal-prep friendly
- Easy to customize with herbs and seasonings
- Ready in under 40 minutes
What Makes Sourdough Starter Work?
Sourdough starter acts as a natural thickener while contributing a subtle tangy flavor that complements earthy mushrooms beautifully. The flour already present in the starter creates a smooth, creamy texture without requiring a traditional flour-based roux. This makes it an excellent way to use excess sourdough discard while adding complexity and depth to homemade soups and sauces.
Prep Time
15 minutes
Cook Time
25 minutes
Total Time
40 minutes
Yield
Approximately 3 cups condensed soup
Equivalent to about 2–3 cans of store-bought condensed cream of mushroom soup.
Ingredients
For the Mushroom Base
- 2 tablespoons unsalted butter
- 1 tablespoon olive oil
- 12 ounces (340g) cremini or button mushrooms, finely chopped
- 1 medium yellow onion, finely diced
- 3 garlic cloves, minced
- 1 teaspoon fresh thyme leaves or ½ teaspoon dried thyme
- ½ teaspoon dried rosemary
- 1 tablespoon soy sauce or Worcestershire sauce
- ½ teaspoon salt
- ¼ teaspoon black pepper
For the Creamy Soup
- 2 cups chicken broth or vegetable broth
- 1 cup whole milk
- ½ cup heavy cream
- ¾ cup sourdough starter discard (100% hydration)
- ¼ teaspoon onion powder
- ¼ teaspoon garlic powder
- Pinch of nutmeg (optional)
Optional Flavor Enhancers
- 2 tablespoons grated Parmesan cheese
- 1 teaspoon mushroom powder
- 1 tablespoon dry white wine
- Fresh parsley for garnish
Equipment
- Large saucepan or Dutch oven
- Wooden spoon
- Whisk
- Immersion blender (optional)
Step-by-Step Instructions
Step 1: Sauté the Aromatics
Heat the butter and olive oil in a large saucepan over medium heat.
Add the diced onion and cook for 4–5 minutes until softened and translucent.
Stir in the garlic and cook for another 30 seconds until fragrant.
The onions should be tender but not browned.
Step 2: Cook the Mushrooms
Add the chopped mushrooms to the pan.
Cook for 8–10 minutes, stirring occasionally.
The mushrooms will first release moisture and then begin to brown as the liquid evaporates.
This stage is crucial because browning develops the deep, savory flavor that gives homemade cream of mushroom soup its signature richness.
Add:
- Thyme
- Rosemary
- Soy sauce or Worcestershire sauce
- Salt
- Black pepper
Cook for 2 additional minutes.
Step 3: Deglaze and Build Flavor
If using white wine, add it now and cook until mostly evaporated.
Pour in the broth and stir well, scraping any browned bits from the bottom of the pan.
Bring the mixture to a gentle simmer.
Allow it to cook for 5 minutes so the flavors can meld together.
Step 4: Prepare the Sourdough Mixture
In a medium bowl whisk together:
- Sourdough starter discard
- Milk
- Heavy cream
- Onion powder
- Garlic powder
- Nutmeg (if using)
Whisk until completely smooth.
This prevents lumps from forming when added to the soup.
Step 5: Thicken the Soup
Reduce heat to low.
Slowly pour the sourdough mixture into the simmering mushroom broth while whisking continuously.
Cook gently for 8–10 minutes.
Avoid boiling vigorously because high heat can cause dairy to separate.
The soup will gradually thicken into a creamy condensed consistency.
Step 6: Blend (Optional)
For a smoother soup:
- Use an immersion blender directly in the pot.
- Blend until partially smooth while leaving some mushroom pieces for texture.
For a rustic version, leave the soup unblended.
Both methods work beautifully.
Step 7: Final Seasoning
Taste and adjust:
- Salt
- Pepper
- Herbs
If desired, stir in Parmesan cheese for extra richness.
Continue cooking for another 1–2 minutes.
Remove from heat.
How Thick Should Condensed Soup Be?
A properly condensed cream of mushroom soup should coat the back of a spoon and appear thicker than a regular soup.
If the soup becomes too thick:
- Add a splash of broth or milk.
If it seems too thin:
- Simmer for a few extra minutes.
- Stir in an additional tablespoon of sourdough discard.
Storage Instructions
Refrigerator
Store in an airtight container for up to 5 days.
Freezer
Freeze for up to 3 months.
Leave about 1 inch of headspace in the container for expansion.
Reheating
Warm gently over low heat.
Add a splash of milk or broth if needed to restore creaminess.
Ways to Use Condensed Cream of Mushroom Soup
This homemade version can replace canned cream of mushroom soup in any recipe.
Casseroles
- Green bean casserole
- Chicken and rice casserole
- Tuna noodle casserole
- Hash brown casserole
Main Dishes
- Chicken pot pie
- Turkey pot pie
- Swedish meatballs
- Beef stroganoff
Sauces and Gravies
- Mushroom gravy
- Creamy pasta sauce
- Slow cooker sauces
- Pan sauces for chicken or pork
Soups
Thin with additional broth to create a delicious mushroom soup.
Expert Tips for Success
✔ Use cremini mushrooms for deeper flavor.
✔ Brown mushrooms thoroughly before adding liquid.
✔ Use mature sourdough discard for more tangy flavor.
✔ Stir continuously while adding the sourdough mixture.
✔ Keep heat low after adding dairy.
✔ Blend only part of the soup for the best texture.
✔ Add Parmesan for extra umami richness.
