This Cream of Mushroom Soup by Katy Holder from her slow cooker vegetarian cookbook is a must-try, made using dried porcini mushrooms, leeks, Swiss brown mushrooms, large mushroom flats, and Madeira.

To make Cream of Mushroom Soup in your slow cooker or crockpot, start by soaking the porcini mushrooms and then combining them with the rest of the ingredients. Cook on high for 2 hours before blending into a smooth, creamy texture.

I often make this soup on chilly days to warm up, Its rich flavors and hearty texture make it a comforting meal that’s both delicious and easy to prepare.

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Can I Use Fresh Porcini Mushrooms Instead of Dried?

Yes, you can use fresh porcini mushrooms if dried ones are not available. Fresh porcini will provide a more subtle flavor compared to the concentrated taste of dried mushrooms. Simply clean and slice them before adding them to the recipe.

Slow Cooker Cream of Mushroom Soup Ingredients

• 10 g (¼ oz) of dried porcini mushrooms
• 1 leek, white part only, washed and thinly sliced
• 200 g (7 oz) of Swiss brown mushrooms, coarsely chopped
• 300 g (10½ oz) of large mushroom flats, coarsely chopped
• 125 ml (4 fl oz/½ cup) of Madeira wine
• 1 liter (35 fl oz/4 cups) of good-quality vegetable stock
• 2 teaspoons of chopped marjoram, plus extra leaves for garnish
• 85 g (3 oz/1/3 cup) of sour cream or crème fraîche
• Crusty bread, to serve

How To Make Slow Cooker Cream of Mushroom Soup

1. Prepare the dried mushrooms: Soak the dried porcini mushrooms in 250 ml (9 fl oz/1 cup) of boiling water for 20 minutes to enhance their flavor.
2. Transfer the mushrooms: Use a slotted spoon to carefully move the soaked porcini mushrooms from their soaking liquid to the slow cooker.
3. Strain the soaking liquid: Pour the mushroom soaking water through a fine-mesh sieve into a jug to filter out any impurities before adding it to the slow cooker.
4. Add remaining ingredients: Place the sliced leek, Swiss brown mushrooms, large mushroom flats, Madeira wine, and vegetable stock into the slow cooker, along with half of the chopped marjoram.
5. Season and cook: Season the mixture generously with sea salt and freshly ground black pepper, cover, and cook on high for 2 hours to develop deep flavors.
6. Purée the soup: Once cooked, use a stick blender to blend the soup directly in the slow cooker until it achieves a smooth consistency.
7. Finalize and serve: Stir in the sour cream or crème fraîche along with the remaining marjoram, cook for another 5 minutes, then check the seasoning before serving with crusty bread garnished with marjoram leaves.

How Long Can I Keep the Soup on ‘Keep Warm’ After Cooking?

It’s safe to keep the soup in the ‘Keep Warm’ setting for up to 2-3 hours after cooking. This helps maintain the soup’s temperature without overcooking the ingredients, ensuring it stays hot until ready to serve.

Recipe Tips

• Enhance the umami flavor: Before adding them to the slow cooker, sauté the mushrooms in a combination of butter and olive oil until they’re golden brown, which enhances their umami richness.
• Lighten the creaminess: Substitute half of the sour cream or crème fraîche with Greek yogurt to cut down on fat and add a tangy flavor, making the soup lighter but still creamy.
• Richer soup base: Roast the vegetable stock with garlic and rosemary at 375°F for 30 minutes before using it in your soup to deepen the flavors.
• Experiment with herbs: Try replacing marjoram with thyme or sage to explore different herbal notes that complement the mushrooms.

Recipe Variations

• Make it vegan: Use coconut cream or soy-based sour cream instead of dairy and ensure the vegetable stock is vegan to cater to vegan dietary preferences.
• Add protein: Incorporate cooked, diced chicken breast or shredded rotisserie chicken into the soup before blending to add texture and protein.
• Add warmth and spice: Mix in a teaspoon of smoked paprika or a pinch of cayenne pepper during cooking to add a subtle heat that complements the mushrooms.
• Try different wines: If Madeira isn’t available, substitute with dry sherry or a splash of white wine to still achieve a deep flavor profile.
• Incorporate extra vegetables: Add chopped carrots or celery at the start of cooking to introduce a slight sweetness and varied texture to the soup.

What To Serve With Cream of Mushroom Soup

I love pairing Cream of Mushroom Soup with robust, savory sides like roasted garlic ciabatta, parmesan crisps, and a tangy arugula salad. Try including caramelized onion tartlets and a side of sautéed asparagus for a delightful variety.

You can also pair your soup with stuffed mushrooms, truffle oil drizzled bruschetta, and a refreshing beetroot carpaccio.

How To Store Leftover Cream of Mushroom Soup

In The Fridge:

Store leftover Cream of Mushroom Soup in an airtight container to keep it fresh. Make sure the soup cools to room temperature before refrigerating. I suggest you consume the refrigerated soup within three to four days for the best taste and food safety.

In The Freezer:

I generally advise against freezing Cream of Mushroom Soup because the cream base may separate and become grainy upon thawing and reheating. If you must freeze, understand the texture might change, which can affect the creaminess.

How To Reheat Leftover Cream of Mushroom Soup

Reheat your leftover Cream of Mushroom Soup by warming it slowly over medium heat on the stove, stirring occasionally to maintain its creamy texture. If I were in your place, I would avoid using high heat as it can cause the soup to separate.

For a quick reheat, the microwave works fine—heat in short intervals, stirring in between to keep the soup smooth.

Check out More Slow Cooker Recipes:

• Slow Cooker Kangaroo Tail Soup
• Slow Cooker Minestrone Soup
• Slow Cooker Chicken Noodle Soup