
How to Make Mushroom & Caramelized Onion Soup
Step 1: Caramelize the Onions
- Heat the butter and olive oil in a large skillet over medium heat.
- Add the sliced onions and sprinkle with salt. Stir to coat the onions evenly in the butter and oil.
- Reduce the heat to medium-low and cook the onions for 30–40 minutes, stirring occasionally, until they turn golden brown and caramelized. (If needed, add a teaspoon of sugar to speed up the process or a splash of water if the onions start to stick.)
Step 2: Cook the Mushrooms
- In a large soup pot, melt the butter over medium heat.
- Add the sliced mushrooms and cook for 8–10 minutes, stirring occasionally, until they release their liquid and begin to brown.
- Stir in the minced garlic and thyme, cooking for another 1–2 minutes until fragrant.
Step 3: Deglaze the Pot
- If using white wine, pour it into the pot and scrape the bottom to release any browned bits. Let it simmer for 1–2 minutes to cook off the alcohol.
Step 4: Combine Onions and Broth
- Add the caramelized onions to the pot with the mushrooms.
- Pour in the vegetable or chicken broth and bring the mixture to a gentle simmer. Let it cook for 15–20 minutes to meld the flavors together.
Step 5: Thicken the Soup
- In a small bowl, whisk the flour into the heavy cream until smooth. Slowly stir this mixture into the soup.
- Cook for another 5–10 minutes, stirring occasionally, until the soup thickens slightly.
Step 6: Blend and Adjust Seasoning
- For a smooth soup, use an immersion blender to puree the mixture to your desired consistency. (If you prefer it chunkier, only blend a portion of the soup.)
- Taste and adjust with additional salt and pepper as needed.
Step 7: Serve and Garnish
- Ladle the soup into bowls and garnish with fresh parsley, croutons, and a sprinkle of Parmesan or Gruyère cheese. Serve with a slice of toasted bread for dipping.
Tips for the Best Mushroom & Caramelized Onion Soup
- Choose the right mushrooms: A mix of mushrooms, like cremini and shiitake, will add more depth to the soup.
- Don’t rush the onions: Caramelizing onions takes time but is worth the effort for their rich, sweet flavor.
- Make it vegan: Substitute the butter with olive oil, use plant-based milk or cream, and choose vegetable broth for a vegan version.
- Balance the flavors: A splash of balsamic vinegar or a squeeze of lemon at the end of cooking can enhance the soup’s flavor.
Why You’ll Love This Recipe
- Rich and savory: The caramelized onions and mushrooms bring a depth of flavor that’s comforting and indulgent.
- Versatile: Serve it as a starter, side dish, or a light main course.
- Easy to customize: You can adjust the creaminess, seasoning, or garnish to suit your taste.
- Great for leftovers: This soup tastes even better the next day as the flavors continue to develop.
Serving Suggestions
Pair this decadent soup with:
- A fresh garden salad
- A warm, crusty baguette or sourdough bread
- A glass of dry white wine or sparkling water with lemon
Storage and Reheating Tips
- Refrigerator: Store leftovers in an airtight container for up to 3 days.
- Freezer: This soup freezes well for up to 2 months, but freeze it before adding the cream for best results. Thaw overnight in the fridge and stir in the cream when reheating.
- Reheating: Warm on the stovetop over low heat or in the microwave, stirring frequently to prevent curdling.








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