Cauliflower Mushroom Soup

Cauliflower Mushroom Soup is a savory soup to make in the Instant Pot that’s delicious with Parmesan Cheese added at the table. My sister Pam’s family loves this tasty soup, and this can easily be vegetarian if you make it with vegetable broth!

Pin the Cauliflower Mushroom Soup to make it later!

Cauliflower Mushroom Soup is a creamy soup that I loved when I first made it, and my sister Pam also enjoyed this soup when I tried it out on her. But this was a recipe where the original photos didn’t show the soup off in all it’s tasty deliciousness. So Kara and I decided to update the recipe and take new photos.

And I don’t apologize for the way we always want to improve the recipe when we’re updating with better photos! We made a few simple changes in this Cauliflower Mushroom Soup recipe to bump up the flavor even more. If anyone was a fan of the original version, you can still find that in the NOTES section of the complete recipe below.

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 without adding many carbs. And making it in the Instant Pot made this an easy recipe. Whether you make the soup vegetarian or use chicken broth, I hope you try it soon!

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 with ingredient amounts.)

• onion
• Olive Oil (affiliate link)
• Minced Garlic (affiliate link)
• Dried Thyme or Ground Thyme (affiliate links)
• Spike Seasoning (affiliate link)
• salt (optional)
• soy sauce or reduced sodium soy sauce. Use Gluten-Free Soy Sauce if needed. (affiliate link)
• heavy cream (or use half and half or milk)
• mushrooms
• cauliflower
• canned vegetable broth (affiliate link) or canned chicken broth (affiliate link)
• cornstarch (optional)
• freshly grated Parmesan cheese

What mushrooms did we use for 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, but use any type of mushroom you prefer.

Why I didn’t cook the mushrooms in the Instant Pot:

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

Do you need cornstarch to thicken this 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.

How low in carb is this Cauliflower Mushroom Soup?

I was pleasantly surprised that even with the optional cornstarch this soup had only 8 net carbs per serving with 7 grams of protein. I didn’t tag this recipe for Keto because it didn’t have much fat and Keto diet followers might not want to use even a small amount of cornstarch. But some people might find it fine for Keto, especially if you skip the cornstarch.

What size Instant Pot did I use?

I use a 6 Quart Instant Pot (affiliate link) for all my Instant Pot Recipes. Check out my growing collection of Instant Pot Recipes on the blog!

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. (Or cook mushrooms in the Instant Pot.)
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. I recommend 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. (Cornstarch is 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

Make it a Low-Carb Meal:

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

More Delicious Instant Pot Soups:

Check out Low-Carb and Keto Instant Pot Soups for more tasty ideas for low-carb soup made in the Instant Pot.

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!

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Yield: 8 servings

Cauliflower Mushroom Soup

Prep Time 15 minutes

Cook Time 5 minutes

Additional Time 30 minutes

Total Time 50 minutes

Cauliflower Mushroom Soup is a delicious savory cauliflower soup for mushroom fans! And this soup is made in the Instant Pot, and if you use vegetable broth it can easily be vegetarian.

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 vegetable broth (or chicken broth)
• 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 Cauliflower Mushroom Soup 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.

This soup with good with chicken broth if you don't care whether it's vegetarian.

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.

Low-Carb Cauliflower and Mushroom Pressure Cooker Soup with Parmesan (original recipe made in electric pressure cooker)

Ingredients:

• 1 large onion, chopped
• 1 tsp. + 1 tsp. olive oil
• 1 T crushed or minced garlic
• 1 tsp. dried thyme
• 1 lb. Cremini (Baby Bella) mushrooms, washed and chopped
• 4 cups chopped cauliflower (1 large head)
• 6 cups vegetable or chicken stock
• 3/4 cup freshly grated Parmesan cheese
• (additional grated Parmesan or light sour cream for adding at the table - optional)

Instructions:

Heat 1 teaspoon of olive oil in the bottom of the pressure cooker (or in a non-stick frying pan).

Add the onions and saute until they're starting to brown, about 5-7 minutes. (Use the saute setting on the electric pressure cooker or medium-high heat on the stove.)

Add the minced garlic and thyme and cook 1-2 minutes more.

Put onions in a bowl (or add them to the pressure cooker if you used a pan to saute the onions.)

Heat the other teaspoon of olive oil and saute the mushrooms until they're lightly browned and all the liquid is evaporated, about 5 minutes.

Put the onion mixture, mushrooms, cauliflower, and stock into the pressure cooker and set to cook for 5 minutes time at high pressure. (For stovetop pressure cooker, bring to high pressure and cook 5 minutes.)

I let the pressure release naturally because I wasn't in a hurry, but you can also use the quick release method.

Use an Immersion Blender to puree the soup, leaving it a little chunky if you prefer. (You can also puree in a food processor or blender, but be careful with the hot liquid if you use one of those.)

Add the 3/4 cup Parmesan and simmer 5-10 minutes, or until all the cheese has melted into the soup.

Serve hot, with freshly-grated Parmesan cheese or sour cream to add at the table.

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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Did you make this recipe? Please leave a star rating (under the PRINT button in the recipe) or share a photo of your results on Instagram! THANKS!

Low-Carb Diet / Low-Glycemic Diet / South Beach Diet Suggestions:
This 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 recipe for cauliflower and mushroom soup 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 better flavor and updated with new photos in 2022 and last updated with more information in 2026.