Decadent Mushroom & Caramelized Onion Soup Recipe

If you’re looking for a bowl of pure comfort that’s both earthy and elegant, Mushroom & Caramelized Onion Soup is your answer. This luxurious soup combines the deep, savory flavors of caramelized onions and mushrooms with a creamy, velvety texture. It’s perfect for chilly evenings, an indulgent appetizer, or a soul-warming main course.

With just a few simple ingredients and a bit of patience to let the onions caramelize to perfection, you can create a restaurant-quality soup at home. Let’s dive into this rich and flavorful recipe.

Ingredients

Here’s what you’ll need to make 4–6 servings of Mushroom & Caramelized Onion Soup:

For the caramelized onions:

• 3 large yellow onions, thinly sliced
• 2 tablespoons unsalted butter
• 1 tablespoon olive oil
• ½ teaspoon salt
• 1 teaspoon sugar (optional, for faster caramelization)

For the soup:

• 3 tablespoons unsalted butter
• 1 pound mushrooms (cremini, button, or a mix), thinly sliced
• 3 cloves garlic, minced
• 1 teaspoon fresh thyme (or ½ teaspoon dried thyme)
• ¼ cup dry white wine (optional, for added depth)
• 4 cups vegetable or chicken broth
• 1 cup heavy cream (or milk for a lighter version)
• 2 tablespoons all-purpose flour (or cornstarch for gluten-free)
• Salt and black pepper, to taste

For garnish:

• Fresh parsley, chopped
• Croutons or toasted bread
• Shaved Parmesan or Gruyère cheese

INSTRUCTIONS:

How to Make Mushroom & Caramelized Onion Soup

Step 1: Caramelize the Onions

1. Heat the butter and olive oil in a large skillet over medium heat.
2. Add the sliced onions and sprinkle with salt. Stir to coat the onions evenly in the butter and oil.
3. 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

1. In a large soup pot, melt the butter over medium heat.
2. Add the sliced mushrooms and cook for 8–10 minutes, stirring occasionally, until they release their liquid and begin to brown.
3. Stir in the minced garlic and thyme, cooking for another 1–2 minutes until fragrant.

Step 3: Deglaze the Pot

1. 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

1. Add the caramelized onions to the pot with the mushrooms.
2. 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

1. In a small bowl, whisk the flour into the heavy cream until smooth. Slowly stir this mixture into the soup.
2. Cook for another 5–10 minutes, stirring occasionally, until the soup thickens slightly.

Step 6: Blend and Adjust Seasoning

1. 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.)
2. Taste and adjust with additional salt and pepper as needed.

Step 7: Serve and Garnish

1. 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

1. Choose the right mushrooms: A mix of mushrooms, like cremini and shiitake, will add more depth to the soup.
2. Don’t rush the onions: Caramelizing onions takes time but is worth the effort for their rich, sweet flavor.
3. Make it vegan: Substitute the butter with olive oil, use plant-based milk or cream, and choose vegetable broth for a vegan version.
4. 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.