Mushroom Soup

Mushroom Soup

Mushroom soup is easy to make at a mediocre level and hard to make at a good one, and the difference lies almost entirely in one stage: what happens to the mushrooms in the pan before they meet any liquid. Mushrooms that steamed in their own juices give a pale, milky soup; mushrooms that truly browned give a dark, deep soup.

Mushrooms are an especially low-calorie vegetable — about 22 calories per 100 grams — and yet a bowl of mushroom soup is usually one of the richest bowls in the category. The reason is simple: almost none of the calories in this soup come from the mushrooms.

Prep time: 15 minutes · Cook time: 35 minutes · Total: about 50 minutes · Yield: 6 servings · Difficulty: easy-medium

The two principles that make it a real mushroom soup

Don’t crowd the pan. Mushrooms are about 90% water. When you put 700 grams of mushrooms into the pot all at once they release all their water, the temperature drops below the browning threshold, and they stew in their own liquid instead of browning. Browning — the Maillard reaction — is all the flavor here, so fry in two or three batches, in a wide pot over high heat, and stir as little as possible.

Dried mushrooms are a real shortcut. 15-20 grams of dried porcini soaked in boiling water give you two things: the mushrooms themselves, and above all the soaking water — a liquid saturated with glutamate and nucleotides, which is the single factor that most deepens a mushroom soup. Don’t throw out the soaking water; strain it through cloth and add it to the pot (the grit sinks to the bottom).

Ingredients (for 6 servings)

• 700 grams fresh mushrooms — button, portobello or a mix — sliced
• 20 grams dried porcini mushrooms + 250 ml boiling water for soaking
• 2 tablespoons butter (about 28 grams)
• 1 tablespoon olive oil
• 1 medium onion, finely chopped
• 2 cloves garlic, crushed
• 1 teaspoon fresh thyme (or 1/2 teaspoon dried)
• 2 tablespoons flour (about 16 grams)
• 100 ml dry white wine — optional
• 1 liter vegetable or chicken stock
• 150 ml heavy cream 38%
• Salt, freshly ground black pepper, a pinch of nutmeg
• Chopped parsley for serving

Choosing ingredients and substitutes

Button and portobello mushrooms are available in the supermarket and work as a mix or on their own. If you have no dried porcini, add 150 grams of fresh mushrooms and another 250 ml of water in place of the dried mushrooms and the soaking water. Fry the extra mushrooms together with the fresh ones. You can replace the 150 ml of 38% cream with the same amount of 15% cooking cream; the soup will be less rich.

Method

1. Soak the dried mushrooms. If you chose the fresh-mushroom alternative, skip the soaking and set aside 250 ml of water for step 6. If using dried: pour 250 ml of boiling water over them and leave for 15-20 minutes. Take them out, chop them, and strain the liquid through cloth or a fine sieve — set it aside.
2. Brown the mushrooms in two batches. Heat half the butter with the olive oil in a wide pot over high heat. Add half the mushrooms in a single layer and fry for 5-6 minutes, barely stirring, until golden brown. Transfer to a plate and repeat with the rest. This is the step that decides the result.
3. Fry the onion and garlic. Return the rest of the butter to the pot, add the onion and fry for 5 minutes until translucent. Add the garlic and thyme and stir for half a minute.
4. Add the flour. Sprinkle in the flour and stir for a full minute over medium heat, so that the raw flour taste disappears.
5. Pour in the wine and scrape. Add the wine and scrape the bottom of the pot with a wooden spoon — all the brown layer stuck there is flavor, and it dissolves into the liquid in a second.
6. Simmer. Return the browned mushrooms, add the stock and the chopped porcini with the strained soaking water, if using them. With the fresh-mushroom alternative, add 250 ml of water instead. Bring to a gentle boil and cook for 20 minutes over low heat.
7. Blend partially. Blend about two thirds of the soup with an immersion blender and leave some pieces. If you want a full cream soup, blend everything.
8. Add the cream and heat for 3 minutes without boiling — boiling cream may separate. Season with salt, black pepper and a pinch of nutmeg, and serve with parsley.

Nutrition facts and calorie estimate

The recommended serving is a bowl of about 300 ml, a sixth of the pot.

The breakdown here tells you more than the total. The 700 grams of mushrooms — the whole pot’s worth — come to only about 25 calories per serving. The butter, olive oil and cream come to about 140 calories per serving. In other words, about seventy percent of this soup is the fat added to it, and the vegetable itself is less than 15%.

So every change to the fat transforms the serving completely, while changing the amount of mushrooms hardly changes anything:

The upside of the mushrooms themselves is not about calories: they are one of the few non-animal dietary sources of selenium and B vitamins, and mushrooms exposed to UV light also provide vitamin D — very rare in plant foods.

Variations and tips

• Vegan version: olive oil instead of butter and light coconut milk instead of cream. About 150 calories per serving, and the taste barely suffers when the mushrooms were properly browned.
• No flour: leave out the flour and blend the soup completely — the mushrooms themselves give enough body. Also suitable for people avoiding gluten.
• No porcini: replace with 10 grams of dried shiitake mushrooms, or add a teaspoon of miso at the end (off the heat). Both supply the same layer of umami.
• Fresh mushrooms — to wash or not: wipe them with a damp cloth and don’t soak them in water. A mushroom absorbs water and then won’t brown at all.
• Making ahead: only 3 days in the fridge, because of the cream. For freezing, make it without the cream and add it after reheating — cream frozen in soup tends to separate into grains.

Summary

A good mushroom soup really comes down to two things: real browning of the mushrooms in two batches, and soaking water from dried mushrooms that wasn’t poured down the sink. The mushrooms themselves are less than 15% of the calories in the bowl, so anyone who wants a lighter soup should touch the cream, not the amount of mushrooms. For more soups see Soups, and for the nutritional values of the vegetable itself — mushrooms.