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Instant Pot Cauliflower Mushroom Soup is a savory low-carb soup that’s extra good with freshly-grated Parmesan added at the table. My sister Pam’s family loves this tasty soup with cauliflower and mushrooms, and so do I!

Pin the Cauliflower Mushroom Soup to make it later!

Instant Pot Cauliflower Mushroom Soup shown in two serving bowls with Parmesan cheese

I loved this low-carb Instant Pot Cauliflower Mushroom Soup, and so did my sister Pam when I tried it out on her a few years ago. But this was definitely a recipe where the original photos didn’t show the soup off in all it’s tasty loveliness. So recently Kara and I decided to update the recipe and take new photos. 

This soup was partly inspired by Cafe Zupas Wisconsin Cauliflower Soup, a rich and creamy and decidedly not diet-friendly soup! Mushrooms were the perfect umami-adding ingredient to bump up the flavor, and making it in the Instant Pot made this an easy recipe. 

And I don’t apologize for the way Kara and I always want to improve the recipe when we’re updating to take better photos, and we made a few simple changes in this recipe to bump up the flavor even more for the updated version. If anyone was a fan of the original version, you can still find that here.

What ingredients do you need for this recipe?

(This is only a list of ingredients; please scroll down for complete printable recipe. Or if you use the JUMP TO RECIPE link at the top of the page, it will take you directly to the complete recipe.)

What mushrooms did we use for the Cauliflower Mushroom Soup?

We used brown Cremini mushrooms (sometimes called Baby Bellas) for this soup. They added a nice flavor and a bit of color too, but you can use any type of mushroom you prefer.

Why don’t I cook the mushrooms in the Instant Pot?

Of course you could cook the mushrooms in the Instant Pot after you saute the onions if you really hate the idea of using another pan. But getting the mushrooms nicely browned and evaporating all the liquid that’s released when the mushrooms cook is important for the flavor in this soup, and I feel that works better in a large frying pan on the stove.

Do you need cornstarch to thicken soup?

The original recipe for this Cauliflower Mushroom Soup didn’t use cornstarch. But when we added a few more ingredients for flavor and creaminess, we liked it best with just one tablespoon of cornstarch mixed with water for a slight bit of thickening. If you prefer not to use cornstarch, it will still taste good but you’ll have a slightly thinner soup.

Can this Cauliflower Mushroom Soup be Keto?

I didn’t tag this recipe as Keto because it didn’t have much fat and my preferred version used a small amount of cornstarch. But when I calculated the nutritional information I was pleasantly surprised that it only had 8 net carbs per serving. Some people might find it to be fine for Keto, especially if you skip the optional cornstarch.

Can this Cauliflower Mushroom Soup be vegetarian?

If you use vegetable broth, this tasty soup can easily be vegetarian.

More Delicious Instant Pot Soups:

Check out Low-Carb and Keto Instant Pot Soups on Kalyn’s Kitchen or Low-Carb Instant Pot Soup Recipes on Slow Cooker or Pressure Cooker for more tasty ideas for low-carb soup made in the Instant Pot.

Love Your Instant Pot?

I use a 6 Quart Instant Pot (affiliate link) for all my Instant Pot Recipes. Check out my growing collection of Instant Pot Recipes! You can also find lots and lots more ideas for the Instant Pot on my Slow Cooker or Pressure Cooker site.

Instant Pot Cauliflower Mushroom Soup process shots collage

How to Make Instant Pot Cauliflower Mushroom Soup:

(This is only a summary of the steps for the recipe; please scroll down for complete printable recipe. Or if you use the JUMP TO RECIPE link at the top of the page, it will take you directly to the complete recipe.)

  1. Heat oil in the Instant Pot on SAUTE, MEDIUM and cook onions. Add minced garlic, dried thyme (or ground thyme), and Spike Seasoning and cook a few minutes more. 
  2. While onions cook, wash mushrooms and cut into quarters.
  3. Heat oil in a large frying pan. Cook mushrooms until they’re nicely browned and released liquid has evaporated. 
  4. Cut up 4 cups of small cauliflower pieces.
  5. Put cooked mushrooms, cauliflower, soy sauce, and chicken or vegetable broth into Instant Pot.
  6. Set the Instant Pot to MANUAL, HIGH PRESSURE, 5 minutes.
  7. When time is up let the pressure release naturally 10 minutes, then release the rest of the pressure.
  8. Here’s how the soup looked when we took off the lid.
  9. Use an Immersion Blender (affiliate link) to puree the soup. 
  10. Set Instant Pot to SAUTE, LOW and stir in the heavy cream, half and half, or milk and let it heat.
  11. Then mix cornstarch with water, stir it in, and let soup cook to thicken for a minute or two. (optional)
  12. Be sure soup is not boiling, and then add 3/4 cup of Parmesan cheese and let it cook until all the cheese has melted.
  13. Season soup to taste with salt and fresh-ground black pepper. (You may not want much salt.)
  14. Serve the Cauliflower Mushroom Soup hot, with more freshly-grated Parmesan cheese to add at the table

Instant Pot Cauliflower Mushroom Soup in two soup bowls with Parmesan cheese, close-up photo

Make it a Low-Carb Meal:

This Cauliflower Mushroom Soup would be delicious with toasted Almond Flour Savory Bread or Olive Bread for a low-carb meal!

Weekend Food Prep:

This Cauliflower Mushroom Soup recipe has been added to a category called Weekend Food Prep where you’ll find recipes you can prep or cook on the weekend and eat during the week!

Instant Pot Cauliflower Mushroom Soup shown in two serving bowls with Parmesan cheese
Yield: 8 servings

Instant Pot Cauliflower Mushroom Soup

Prep Time 15 minutes
Cook Time 5 minutes
Additional Time 30 minutes
Total Time 50 minutes

This low-carb Instant Pot Cauliflower Mushroom Soup is a delicious savory cauliflower soup for mushroom fans!

Ingredients

  • 1 onion, chopped
  • 2 tsp. + 1 T olive oil
  • 1 T minced garlic
  • 1 tsp. dried thyme (or slightly less ground thyme)
  • 1 tsp. Spike Seasoning
  • 1 lb. Cremini mushrooms, washed and chopped
  • 4 cups chopped cauliflower (see notes)
  • 2 T soy sauce (see notes)
  • 6 cups chicken broth (see notes)
  • 1/4 cup heavy cream (see notes)
  • 1 T cornstarch mixed with 1 T water (optional)
  • salt and fresh-ground black pepper (to taste)
  • 3/4 cup freshly grated Parmesan cheese, plus more for adding at the table if desired

Instructions

  1. Heat 2 tsp. oil in the Instant Pot on SAUTE, MEDIUM and cook onions until they're starting to barely brown, about 5 minutes.
  2. Then add minced garlic, dried thyme or ground thyme, and Spike Seasoning and cook about 2 minutes more. (I like to use a slightly smaller amount of ground thyme, but regular dried thyme is fine. If you don't have Spike Seasoning, use any all-purpose seasoning blend.)
  3. While onions cook, wash mushrooms if needed, cut up mushrooms into quarters, and heat 1 T oil in a large frying pan on the stove.
  4. Cook mushrooms until they're nicely browned and any released liquid has evaporated. (You can cook the mushrooms in the Instant Pot, but I think browning the mushrooms and evaporating the liquid works better in a pan on the stove.)
  5. Cut up 4 generous cups of small cauliflower pieces.
  6. Put the cooked mushrooms, cauliflower, soy sauce, and chicken or vegetable broth into the Instant Pot.
  7. Set the Instant Pot to MANUAL, HIGH PRESSURE, 5 minutes.
  8. When time is up let the pressure release naturally for 10 minutes, then release the rest of the pressure.
  9. Then use an Immersion Blender (affiliate link) to puree the soup, leaving it a little chunky if you prefer. (You can also puree in a food processor or blender, but the immersion blender is much easier.)
  10. Set Instant Pot to SAUTE, LOW and stir in the heavy cream, half and half, or milk and let it heat through.
  11. Then mix 1 T cornstarch with 1 T water, stir it in, and let the soup cook to thicken for a minute or two. (This is optional if you don't mind a slightly thinner soup.)
  12. Be sure the soup is not boiling and not too hot, and then add 3/4 cup of Parmesan cheese and let it melt for 5 minutes, or until all the cheese has melted into the soup.
  13. Season soup to taste with salt and fresh-ground black pepper. (Soy sauce adds sodium so you might not want much salt.)
  14. Serve hot, with more freshly-grated Parmesan cheese to add at the table

Notes

You don't have to have exactly four cups of chopped cauliflower; just use 1 large head of cauliflower.

Use chicken broth or vegetable broth, whichever you prefer.

Use low-sodium soy sauce if you prefer. Be sure to use gluten-free soy sauce if needed.

Use half and half or milk instead of heavy cream if you prefer.

Recipe created by Kalyn when she was slightly infatuated with her new electric pressure cooker.

Nutrition Information

Yield

8

Serving Size

1
Amount Per Serving Calories 132Total Fat 8gSaturated Fat 3gTrans Fat 0gUnsaturated Fat 3gCholesterol 20mgSodium 1360mgCarbohydrates 10gFiber 2gSugar 4gProtein 7g

Nutrition information is automatically calculated by the Recipe Plug-In I am using. I am not a nutritionist and cannot guarantee 100% accuracy, since many variables affect those calculations.

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© Kalyn Denny
Category: Instant Pot
Instant Pot Cauliflower Mushroom Soup shown in two bowls with spoons and Parmesan.

Low-Carb Diet / Low-Glycemic Diet / South Beach Diet Suggestions:
Instant Pot Cauliflower Mushroom Soup would be approved for low-carb eating plans, as well as all phases of the original South Beach Diet. Check nutritional information to see if you would eat this for Keto. Low-carb diets would want heavy cream and plenty of cheese; the South Beach Diet would recommend low-fat milk and a moderate amount of Parmesan cheese.

Find More Recipes Like This One:
Use Instant Pot Recipes to find more recipes like this one. Use the Diet Type Index to find recipes suitable for a specific eating plan. You might also like to follow Kalyn’s Kitchen on Pinterest, on Facebook, on Instagram, on TikTok, or on YouTube to see all the good recipes I’m sharing there.

Historical Notes for this Recipe:
This Cauliflower Mushroom Soup recipe was first posted in 2014 when I had a new electric pressure cooker (after using a stovetop pressure cooker for a few years.) The recipe was improved for even better flavor and updated with new photos in 2022 and updated again with more information in 2024.

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