Caramelized Onion, Fennel and Mushroom Soup – Umami in a Bowl

What do you make when you want something hearty but light? Something that will warm the cockles of your heart but not make you feel stuffed? That will work for a light and early pre-theater dinner after a not so light afternoon lunch with your sister who was just in for the afternoon? (What a treat!)

You make this soup.

The Umami is strong with this one

I love onion soup, but never found it satisfying on its own without being topped with a ton of cheese and bread.

This soup is different. Between the mushrooms, fennel and beef broth, it’s packed with umami. Add some shaved parmesan and you’re in an umami paradise, and satiated beyond what you might have expected from something this light.

What is Umami?

Umami is the so-called fifth taste, imparting a savoriness that harmonizes with other flavors and enhances the deliciousness and satiating effect of foods.

I love this definition of umami – It describes what all good food should do, and exactly how I felt after eating this wonderful soup.

“It’s something that’s kind to the body.. “It’s mild, and, after eating, it’s not heavy on your stomach. It helps you wake up better in the morning. That’s what deliciousness is about. It’s about feeling good after eating.”

The chemical in food responsible for umami is free glutamate, which occurs naturally in certain foods, especially Japanese kelp and seaweed, but also tomatoes, aged cheeses, fish and soy sauces, shrimp and certain other fish. Mothers milk is also rich in glutamate. Food proteins are rich in glutamate, but this glutamate cannot be tasted. However, if you ferment protein, proteolysis frees up the glutamate – so fermented foods are also rich in umami.

5′-Inosinate and 5′-guanylate have also been found to have umami. They are synergistic with glutamate, such that their combination with glutamate is much stronger than any of the the three are individually in triggering umami. It’s why beef broth (an inosinate source) made with glutamate rich foods such as onion, tomato and carrot tastes so much better to us than just plain beef broth.

Dried mushrooms are rich in 5′-guanylate. But soaking them in boiling water, as many recipes dictate, decomposes the guanylate. So soak them in cold water if you want them for umami. (Some argue mushrooms are best soaked in cold water overnight in the fridge, but that’s more advance prep than I can do.) Pair them with beef broth or onions to get that umami synergy.

Probably the richest Umami you can get is in the Kombu Dashi – a Japanese broth made from dried seaweed. Typically, dried tuna (bonito), sardine flakes or dried mushrooms are added to the broth – these foods are rich in 5′-Inosinate acid and 5-guanlylate. So Kombu dashi is pure umami.

Salt enhances umami, but only to a point, so don’t over-salt your foods.

Umami rich foods may enhance satiety, as evidenced by the fact that women eating soup enhanced with glutamate eat less at a subsequent meal than those whose soup does not have glutamate. (I can attest to this – this soup filled me so much that I was not hungry for much that entire evening.)

Glutamate rich foods may have other effects beyond mouth taste, mediated via glutamate receptors in the GI tract. For this reason, researchers in Australia are proposing a new category called “alimentary tastes” for newly discovered tastes such as umami and fat.  Given that even the basic tastes of salt and sweet also have actions throughout the body as well as in the mouth, I’m not sure that makes sense. But its an interesting point of view.

What about MSG?

Glutamate is the main ingredient in MSG (monosodium glutamate), a popular food additive.

Unlike natural glutamate-rich food, MSG has gotten a bad rap as a cause of migraine headaches and the so-called “Chinese restaurant syndrome”, though this connection has still not been entirely proven or debunked. In general, I take the approach that more is not necessarily better, and extracting and concentrating any food ingredient is never as good as getting it in its natural form. Plus, I suffer from migraines. So no MSG for me.

One of the strongest arguments against MSG use in my opinion is a recent study showing that use of MSG may attenuate natural umami taste, making eaters less sensitive to detecting the lower levels of natural umami in food.

Go for the Umami

This list of umami-rich foods is a great reference. I for one am going to be referring to it again to find ways to enhance the deliciousness of my foods.

In the meantime, enjoy this soup!

Carmelized Onion, Fennel and Mushroom Soup

I tweaked a recipe from Farideh Sadighen in Saveur by adding dried mushrooms and their broth (hello, umami…), substituting butter for half the olive oil for caramelizing, and suggest substituting vermouth for white wine. Next time I plan to use a beef broth made with some nice short ribs that I will cut up when cooked and add back to the soup.


  • 1 ounce dried porcini mushrooms
  • 1 cup water
  • 3 tbsp. olive oil
  • 2 tbsp butter
  • 3 large yellow onions, thinly sliced
  • 1 large bulb fennel, halved and thinly sliced lengthwise, fronds reserved
  • 2 cloves garlic, minced
  • 8 cups beef stock
  • 1 lb. mixed mushrooms (I used shitake and crimini, roughly chopped)
  • 1⁄4 cup dry white wine or vermouth
  • Salt and freshly ground black pepper
  • Shave Parmesan cheese for garnish (optional)


Soak the dried mushrooms in 1 cup hot water for 20-30 minutes till softened. (If using cold water, you may need to soak up to 2 hours.) Remove the mushrooms, reserving the soaking liquid, and roughly chop them. Strain the liquid through a paper-towel-lined sieve before using.

In a large saucepan, heat 2 tablespoons olive oil and 2 tbsp butter over medium-high heat. Add the onions and fennel and cook, stirring, until soft and caramelized, about 45 mins to an hour. (I found this post and this video helpful in learning how to caramelize onions.) Add the garlic and cook, stirring, until fragrant, 2 minutes. Pour in the beef and mushroom stocks and bring to a simmer over medium heat.

While the onions and fennel are caramelizing, heat 1 tablespoon olive oil over medium-high heat in a 12 inch skillet. Add the mushrooms and cook, stirring, until golden and giving up liquid, about 5-10 minutes. Add the wine or vermouth and cook until slightly reduced, about 5 minutes. If onions still caramelizing, turn off the heat and let rest till next step.

Scrape the mushrooms and wine into the soup and cook, stirring, for about 5 minutes. Season the soup with salt and pepper, ladle into bowls, and garnish with some shaved Parmesan and the reserved fennel fronds.


More on Umami

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.