Light Mushroom Soup with Fresh Herbs

Light mushroom soup is a broth-based soup made with browned mushrooms, onion, garlic, and a small amount of milk rather than a heavy cream base. It is savory and satisfying while staying relatively delicate, and it makes an easy lunch or first course with crusty bread.

Ingredients

1 tablespoon (15 ml) olive oil
1 tablespoon (14 g) unsalted butter
1 medium yellow onion, finely chopped, about 1 cup (150 g)
2 garlic cloves, minced, about 2 teaspoons (6 g)
1 pound (450 g) cremini or button mushrooms, cleaned and sliced about ¼ inch (6 mm) thick
1 teaspoon (5 ml) fresh thyme leaves, or ½ teaspoon (1 g) dried thyme
¼ cup (30 g) all-purpose flour
4 cups (950 ml) low-sodium vegetable broth or chicken broth
1 bay leaf
½ teaspoon (3 g) fine salt, plus more to taste
¼ teaspoon (0.5 g) freshly ground black pepper, plus more to taste
½ cup (120 ml) low-fat milk, warmed slightly
1 teaspoon (5 ml) lemon juice, or to taste
2 tablespoons (8 g) chopped fresh parsley, for serving

Instructions

Prepare the vegetables. Wipe dirt from the mushrooms with a damp paper towel or brush, then slice them. Chop the onion and mince the garlic. Keep the mushrooms dry rather than soaking them; excess water can slow browning. This preparation takes about 15 minutes.
Soften the onion. Warm the olive oil and butter in a large, heavy-bottomed pot over medium heat. Add the onion and cook for 4 to 5 minutes, stirring occasionally, until soft and translucent but not browned. Add the garlic and thyme and stir for 30 seconds, just until fragrant.
Brown the mushrooms. Add the sliced mushrooms and a pinch of the measured salt. Cook uncovered for 8 to 10 minutes, stirring every couple of minutes. The mushrooms will release liquid; continue cooking until most of it evaporates and the slices are tender with some golden edges. If your pot is small, cook the mushrooms in two batches so they brown instead of steam.
Make a light thickener. Sprinkle the flour over the vegetables and stir for 1 minute to coat them evenly and cook away the raw flour taste. Pour in about ½ cup (120 ml) of broth slowly, stirring and scraping the bottom of the pot to make a smooth paste. Gradually stir in the remaining broth.
Simmer the soup. Add the bay leaf, remaining salt, and pepper. Bring the soup just to a gentle simmer, then lower the heat and cook uncovered for 12 to 15 minutes, stirring occasionally. Avoid a hard boil, which can make the broth reduce too quickly and cause the flour to stick.
Add the milk and finish. Remove the bay leaf. Stir in the warmed milk and heat the soup gently for 2 to 3 minutes, without letting it boil. Taste and adjust the salt and pepper, then stir in the lemon juice. Ladle into bowls and finish with parsley. The finished soup should be hot throughout; a thermometer is not required for this vegetable-based recipe.

Tips

Choose mushrooms that fit your budget. Cremini have a deeper flavor than white button mushrooms, but either works. A small handful of shiitakes can add savoriness; remove their tough stems before slicing.
Give the mushrooms room. Crowding traps steam, so the mushrooms may turn soft and pale instead of developing browned edges. Use a wide pot or brown them in batches.
Keep the soup from getting heavy. Warm the milk before adding it and avoid boiling after it goes in. For a thinner soup, use 2 tablespoons (16 g) flour; it will have a looser, more broth-like texture.
Adjust the finish carefully. Broth salt levels vary, so taste before adding extra salt. Lemon juice brightens the flavor, but add it a little at a time so it does not overwhelm the mushrooms.

Serving Suggestions

Serve the soup hot as a light lunch with whole-grain toast, a crusty roll, or a grilled cheese sandwich. For a first course, pour smaller portions and pair them with a crisp green salad dressed with vinaigrette. A little extra parsley, cracked black pepper, or a few thinly sliced sautéed mushrooms makes a simple garnish without adding much richness.

Variations

For a dairy-free version, replace the butter with another tablespoon (15 ml) of olive oil and use unsweetened oat milk or soy milk in place of dairy milk. Choose an unflavored product; sweetened milk changes the savory taste. To make the soup gluten-free, omit the flour and stir 1 tablespoon (8 g) cornstarch into 2 tablespoons (30 ml) cold water. Add the slurry near the end and simmer for 1 to 2 minutes, until lightly thickened.

For a more pronounced woodland flavor, replace up to 2 ounces (55 g) of the fresh mushrooms with rehydrated dried porcini. Soak them in hot water for about 20 minutes, lift them out, chop them, and add them with the fresh mushrooms; strain the soaking liquid through a coffee filter or fine sieve and use it as part of the broth. The result will taste more intensely mushroomy. You can also blend about one-third of the finished soup and stir it back in for a creamier texture without adding more dairy.

Storage and Reheating

Cool leftovers promptly and refrigerate them in a covered, shallow container within 2 hours of cooking. Keep the soup refrigerated for 3 to 4 days. Reheat only the amount you plan to serve in a saucepan over medium-low heat, stirring often until steaming hot throughout; if it has thickened, loosen it with a splash of broth or water. For food safety, leftovers should reach 165°F (74°C) when checked with a food thermometer. Avoid repeatedly heating and cooling the entire batch.

To freeze, cool the soup promptly and transfer it to freezer-safe containers, leaving a little room for expansion. Freeze for up to 2 months for best quality. Thaw overnight in the refrigerator and reheat as above. Milk-based soups can separate slightly after freezing, so stir well as they warm; blending briefly can help restore a smooth texture.

Frequently Asked Questions

Can I make light mushroom soup without flour?
Yes. Leave out the flour for a thinner, clear broth-style soup, or use the cornstarch slurry in the variation above. Do not add dry cornstarch directly to the pot, as it can form lumps.

Can I use vegetable broth?
Yes. Low-sodium vegetable broth keeps the soup vegetarian and lets the mushroom flavor stand out. Chicken broth also works, though it changes the soup from vegetarian to meat-based.

Should I peel mushrooms before cooking?
No. Mushrooms do not need peeling. Brush or wipe off visible dirt and trim any dry ends. Rinsing briefly is acceptable if they are especially dirty, but dry them well before slicing.

Can I make the soup ahead?
Yes. Prepare it up to 3 to 4 days ahead and refrigerate it promptly. For the freshest texture, you can also cook through the simmering step, chill the soup safely, and add the milk and lemon while reheating.

Why is my mushroom soup watery?
Mushrooms release moisture as they cook. Give them time to release and then cook off most of that liquid before adding the flour and broth. If the finished soup is still thinner than you like, simmer it gently for a few extra minutes or use the cornstarch method.

Can I blend all of it?
Yes. Blend carefully in batches if using a countertop blender, leaving space for steam to escape and holding the lid with a folded towel. An immersion blender is convenient, but blending just part of the soup preserves some mushroom slices and texture.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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