Low Carb Watercress and Cauliflower Soup

This low carb watercress and cauliflower soup is silky, bright green and gently peppery, and it comes together with just three main ingredients in about 25 minutes. It's light enough for a starter but cozy enough for lunch, and at around 7g net carbs per serving it's keto-friendly too.

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Watercress doesn't get nearly enough attention. It's a leafy green in the same family as mustard, radish and wasabi, so it brings a gentle, mustardy kick rather than chili heat. That makes it a great fit for families where some people like a little spice and others don't. Blended with cauliflower, it turns into a smooth, velvety soup that tastes like much more work than it is. If you love watercress as much as we do, try our Watercress Salad with Shrimp, Avocado and Cucumber too.

Is Watercress Keto? Watercress Carbs and Nutrition

Yes, watercress is about as keto-friendly as a vegetable gets. It's roughly 95% water, and one cup of chopped raw watercress (about 34g) has only around 0.4g of total carbs and 0.2g of fiber, so just 0.2g net carbs. Even a big 100g handful comes in at roughly 1.3g carbs and under 1g net carbs, which is why it shows up on our list of low carb vegetables.

Those tiny numbers don't mean it's short on goodness. Watercress is an excellent source of vitamin K (a single cup covers most of an adult's daily needs), and it also gives you vitamin C, vitamin A, calcium and potassium. A cup has only about 4 calories, so you can pile it on salads, sandwiches and soups as much as you like.

Most of the carbs in this soup come from the cauliflower and the stock, not the watercress, and the whole bowl still lands comfortably in keto territory.

Key Ingredients & Substitutions

• Frozen cauliflower. It gives the soup its body and creamy texture without any flour or potato, and frozen florets mean no chopping. Fresh cauliflower works just as well: one medium head trimmed into florets is about the same 16 ounces, and may need a few extra minutes to soften.
• Vegetable stock. The stock is where most of the flavor comes from, so use one you enjoy drinking on its own. A low-sodium stock lets you control the salt. Chicken stock or bone broth make a richer soup if you don't need it to be vegetarian. Check the label, since some boxed stocks add sugar or starch.
• Fresh watercress. Look for bright green, perky leaves with no yellowing. Thick lower stems can be stringy, so trim the toughest ones and use the rest, stems and all. If you can't find watercress, baby arugula gives a similar peppery flavor, and baby spinach makes a milder, sweeter soup.
• Salt and pepper. Homemade vegetable soups usually need more seasoning than you'd expect, and how much depends on your stock. Taste and adjust at the end.
• Extra watercress for garnish. A little pile of fresh leaves on top looks pretty and adds a fresh crunch against the smooth soup.

Helpful Tips

Don't overcook the watercress. Simmering it with the cauliflower for 15 minutes is all it needs. Cooking it much longer dulls that vivid green color and the peppery flavor, so take the pan off the heat as soon as the cauliflower is tender.

Blend hot soup safely. If you use a countertop blender (we love our Ninja), fill it no more than halfway, remove the center cap from the lid and cover the hole with a folded kitchen towel so steam can escape. Blending in batches is safer than overfilling.

Or skip the transfer altogether. An immersion blender lets you purée the soup right in the saucepan, which means less mess and fewer dishes. Keep the blade fully submerged to avoid splatters.

Blend longer than you think. For a really silky texture, keep blending for a full minute or two after it looks smooth. If it's thicker than you like, add a splash of hot stock or water; if it's too thin, simmer it uncovered for a few minutes.

Season at the very end. Stock brands vary a lot in saltiness, so wait until the soup is blended before adding salt and pepper. A squeeze of lemon juice at this stage also brightens the flavor beautifully.

Variations

• Creamy watercress soup. Stir in a few tablespoons of heavy cream or a spoonful of cream cheese after blending for a richer, more filling bowl.
• Cheesy version. Melt a handful of shredded sharp cheddar into the hot soup. If you love that idea, you'll also like our Low Carb Broccoli Cheese Soup.
• Garlic and onion. Sauté a couple of garlic cloves and a little chopped onion or leek in butter before adding the other ingredients. Keep the onion to a small amount, since it adds carbs quickly.
• Extra peppery. Add a pinch of cayenne, a little grated horseradish or a teaspoon of Dijon mustard to play up watercress's natural heat.
• Bacon topping. Crumble crispy bacon over each bowl for a salty, smoky crunch that turns it into a heartier lunch.
• Other greens. Swap half the watercress for baby spinach or kale for a milder flavor, or try cauliflower with fennel instead, like our Cauliflower Fennel Soup.

Serving Ideas

This recipe makes four starter-size bowls, which is perfect before a roast chicken, a piece of grilled salmon or a steak dinner. As a main lunch dish it serves two or three, and you'll want something a little more substantial alongside it.

For dunking, a few Almond Flour Crackers or a slice of Very Low Carb Cheese Bread are hard to beat. A swirl of cream or a drizzle of olive oil, a few roasted pumpkin seeds and some extra watercress leaves on top make it look restaurant-ready. Need more midday inspiration? Browse our 100+ Low Carb Lunch Ideas.

Storing & Freezing

Let the soup cool, then keep it in an airtight container in the fridge for up to 3 days. The color may darken slightly over time, but the flavor stays great. Reheat gently on the stovetop over medium-low heat or in the microwave, stirring often, and add a splash of stock if it has thickened. If you added cream or cheese, avoid boiling it so it doesn't separate.

The soup also freezes well for up to 3 months, which makes it a handy make-ahead lunch. Freeze it before adding any cream or cheese, in portion-size containers with a little headspace. Thaw overnight in the fridge, then reheat on the stovetop and whisk or give it a quick blend to bring back the smooth texture. Add a fresh watercress garnish just before serving.

More Low Carb Soups

If you loved this recipe, here are a few more you might enjoy:

• Low Carb Purple Cauliflower Soup
• Low Carb Creamy Turnip Soup
• Low Carb Mushroom Soup
• The Best Low Carb Soup Recipes

📖 Recipe

StepAwayFromTheCarbs.com

Low Carb Watercress and Cauliflower Soup

4.67 from 9 votes

A silky, bright green soup made with cauliflower, vegetable stock and peppery fresh watercress. Ready in about 25 minutes and keto-friendly, it makes a light starter for four or a cozy lunch for two or three.

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Prep Time 5 minutes mins

Cook Time 20 minutes mins

Total Time 25 minutes mins

Makes: 4 servings

Net Carbs: 7

Calories: 43

Ingredients Equipment Method Nutrition Notes

Ingredients

 

US CustomaryMetric

• 16 oz frozen cauliflower or fresh florets
• 4 cups vegetable stock
• 4 oz fresh watercress tough stems trimmed
• salt and pepper to taste
• extra watercress for garnish

Equipment

• Ninja Professional 72oz Countertop Blender, Black

Step-by-Step Instructions

 

Cook ModePrevent your screen from going dark

1. Add the frozen cauliflower, vegetable stock and fresh watercress to a large saucepan. Bring to a boil over medium-high heat.
2. Reduce the heat to low, cover and simmer for 15 minutes, or until the cauliflower is completely tender when pierced with a knife.
3. Remove from the heat. Blend until very smooth with an immersion blender, or carefully transfer to a countertop blender in batches (fill no more than halfway and vent the lid with a towel over it).
4. Return the soup to the saucepan and warm through if needed. Taste and season with salt and pepper. Add a splash of hot stock or water if it's too thick.
5. Ladle into bowls and garnish with a little extra fresh watercress.

Nutrition

Calories: 43kcalCarbohydrates: 9gProtein: 3gFat: 0gSaturated Fat: 0gPolyunsaturated Fat: 0gMonounsaturated Fat: 0gTrans Fat: 0gCholesterol: 0mgSodium: 986mgPotassium: 433mgFiber: 2gSugar: 4gVitamin A: 1402IUVitamin C: 67mgCalcium: 59mgIron: 1mgNet Carbs: 7g

Notes

Season at the end: stock brands vary a lot in saltiness. A squeeze of lemon juice brightens the flavor.

For a creamier soup, stir in a few tablespoons of heavy cream after blending (this adds a little fat and a trace of carbs).

Keeps in the fridge for up to 3 days and freezes well for up to 3 months (freeze before adding any cream).

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Nutritional information is provided as a courtesy and is my best approximation. Net carbs are calculated as the total grams carbs minus the total grams of fiber.