Name: Homemade Keto French Onion Soup Recipe
Prep time: 15 min
Cook time: 1 h
Total time: PT-484033H8M47S
Cuisine: French
Ingredients: 4 large onions, thinly sliced; 4 tbsp unsalted butter (or ghee); 4 cups low-carb beef broth; 1 tbsp garlic, minced; 1 tbsp fresh thyme (or 1 tsp dried); 1/2 cup dry white wine (optional); Salt and pepper, to taste; 1 tbsp Worcestershire sauce (sugar-free); 1/4 tsp xanthan gum (optional, for thickening); 1 cup grated Gruyère or mozzarella cheese; Keto bread slices or cheese crisps for topping

Jump to Recipe·Print Recipe

When it comes to comfort food, French onion soup ranks high on the list. There’s something deeply satisfying about the rich, caramelized onions simmered in a flavorful broth, topped with gooey, melted cheese. But for those following a keto or low-carb lifestyle, traditional French onion soup can be a challenge. The bread, high-carb onions, and sometimes even the broth make it a no-go for keto dieters.

But guess what? We’ve got a keto-friendly version that’ll knock your socks off. It keeps all the delicious flavors you love but swaps out the carb-heavy parts for keto-approved alternatives. And yes, it still comes with a cheese-covered top that’ll have you scraping your bowl for every last bit.

What Makes French Onion Soup Not Keto-Friendly?

Let’s start with the basics. Traditional French onion soup consists of onions, beef broth, a splash of wine or sherry, and a big slice of baguette on top, covered in melted Gruyère cheese. Sounds innocent enough, right? Not exactly.

Here’s the breakdown:

Onions – While onions are natural and packed with nutrients, they’re relatively high in carbs. A whole onion can contain up to 12 grams of net carbs.
Bread – That crispy slice of bread sitting under a thick blanket of cheese? Yeah, that’s pretty much a carb bomb. Not ideal for keto.
Broth – Some store-bought broths can contain hidden carbs, usually from added sugar or starches, which can sabotage your keto game without you even realizing it.

So, the challenge is taking all that deliciousness and giving it a low-carb makeover. And guess what? It’s totally doable!

How to Make a Keto-Friendly French Onion Soup

We’ve made a few swaps and tweaks to keep the carb count in check while still delivering on all the cozy, cheesy goodness. Here’s what we changed:

Onions – We’ll reduce the amount used to cut down on carbs but still give the soup that unmistakable onion flavor.
Broth – We’ll use a high-quality, low-carb beef broth. You can make your own or find a trusted brand at the store (just make sure to check those labels!).
Bread Alternative – We’ll swap out the baguette for a keto-friendly bread or even use cheese crisps to get that crunch without the carbs.
Cheese – No changes here. The cheese is perfect as is. Gruyère, mozzarella, or even a sharp cheddar all work well in this dish.

Now that you know how we’re going to tackle this, let’s jump into the actual recipe!

Keto French Onion Soup Recipe

Ingredients You’ll Need:

4 large onions (yellow or sweet onions work best)
4 tablespoons unsalted butter (or ghee for extra flavor)
4 cups low-carb beef broth (homemade or store-bought, just check the carbs)
1 tablespoon garlic (minced)
1 tablespoon fresh thyme (or 1 tsp dried)
1/2 cup dry white wine (optional, but it adds depth to the flavor)
Salt and pepper (to taste)
1 tablespoon Worcestershire sauce (check for sugar-free)
1/4 teaspoon xanthan gum (to thicken the soup slightly)
1 cup grated Gruyère or mozzarella cheese (more if you want that super cheesy top)
Keto bread slices or cheese crisps (for the topping)

Step-by-Step Instructions:

1. Caramelize the Onions

Caramelizing onions is the foundation of a great French onion soup, keto or not. But it’s not a quick process, so patience is key here.

Start by slicing your onions thinly.
In a large pot, melt the butter over medium heat. Add the onions and cook them slowly, stirring occasionally. It’ll take around 30-40 minutes for the onions to become golden brown and deeply caramelized. If they start to stick or brown too quickly, lower the heat and keep stirring.
Once the onions are nicely caramelized, add the garlic and thyme. Sauté for another 2-3 minutes until fragrant.

2. Deglaze the Pot

Deglazing is a fancy word for adding liquid to lift up all the flavorful bits stuck to the bottom of the pot.

Pour in the dry white wine (if using) and use a wooden spoon to scrape up all those caramelized bits. If you’re skipping the wine, you can deglaze with a little broth instead.
Let the liquid simmer until it’s mostly evaporated, which will take about 5-7 minutes.

3. Simmer the Soup

Now, it’s time to turn these caramelized onions into a soup.

Add the low-carb beef broth, Worcestershire sauce, and a pinch of salt and pepper.
Bring the soup to a boil, then reduce the heat and let it simmer for 20-25 minutes to allow all the flavors to meld together.
If you want your soup a little thicker (closer to the traditional texture), whisk in the xanthan gum. This is totally optional, but it’ll give the soup a slightly thicker, heartier consistency without adding any carbs.

4. Prepare the Keto “Bread” Topping

While your soup is simmering, prep the keto-friendly “bread” for the top. You’ve got a few options here:

Keto Bread Slices – You can either bake or fry up some slices of low-carb bread. Just toast them lightly before adding them to the soup.
Cheese Crisps – If you want to skip the bread altogether, you can use cheese crisps for that satisfying crunch. These are super low-carb and ridiculously easy to make. Simply bake shredded cheese in small rounds at 350°F for about 5-7 minutes until crispy.

5. Assemble the Soup

This is the part where the magic happens—combining everything together.

Preheat your oven’s broiler.
Ladle the soup into oven-safe bowls (French onion soup is traditionally served in those cute little crock-style bowls, but any oven-safe bowl will do).
Top each bowl with a slice of toasted keto bread or a cheese crisp.
Pile on the Gruyère or mozzarella cheese. Don’t be shy here—this is what makes the soup irresistible.

6. Broil Until Bubbly

Pop the bowls under the broiler for 3-5 minutes, or until the cheese is melted, bubbly, and golden brown. Keep an eye on it, because it can go from perfect to burnt pretty quickly!

7. Serve and Enjoy

Carefully remove the bowls from the oven (they’ll be hot!), and serve immediately. The soup will be piping hot, the cheese melty and gooey, and the flavors will have you hooked.

Tips for Making the Best Keto French Onion Soup

Take Your Time with the Onions – The caramelization process can’t be rushed. Low and slow is the way to go if you want that deep, rich flavor.
Pick the Right Broth – A good-quality beef broth is key. Make sure it’s low in carbs and packed with flavor. Homemade broth is always a great option if you’ve got the time.
Wine is Optional – If you’re really strict about your carb count, you can skip the wine. But a dry white wine adds a subtle acidity that balances the sweetness of the onions beautifully.
Be Generous with the Cheese – The more cheese, the better. It’s keto, after all, so feel free to go heavy-handed here.

Nutritional Information (Per Serving)

Here’s a rough estimate of the nutritional breakdown for one serving of Keto French Onion Soup:

Calories: 280
Fat: 22g
Carbs: 6g (Net Carbs: 4g)
Protein: 12g

Of course, this can vary slightly depending on the brand of broth or cheese you use, but it’s pretty low-carb across the board. You can definitely fit this into your keto meal plan without any guilt.

Why This Keto French Onion Soup is Perfect for Your Diet

Not only does this recipe satisfy those cravings for a classic French onion soup, but it’s also designed to keep you firmly in ketosis. The reduced carbs in this recipe mean you can enjoy it without spiking your blood sugar or knocking yourself out of fat-burning mode.

Plus, onions, despite their carb content, bring a ton of health benefits. They’re loaded with antioxidants and compounds that support heart health, immune function, and even cancer prevention. So, while this soup may seem indulgent, it’s actually packing some serious nutritional punch.

Variations to Try

Feeling adventurous? Here are a few twists on the classic Keto French Onion Soup:

Add Protein – Want to make it more filling? Add some shredded rotisserie chicken or thinly sliced beef to the soup.
Spice It Up – Toss in a dash of hot sauce or red pepper flakes to give your soup a little kick.
Make it Dairy-Free – Swap out the cheese for a dairy-free option and use a vegan butter or coconut oil to caramelize the onions.

Conclusion

Keto French onion soup is not just a great way to enjoy a comfort food classic without wrecking your carb count—it’s also an opportunity to experiment and play around with your favorite low-carb ingredients. Whether you stick to the recipe or put your own spin on it, this soup is bound to become a regular in your keto meal rotation. It’s cozy, cheesy, and deeply satisfying.

So, grab those onions, fire up your stove, and get ready to enjoy a delicious keto twist on an old favorite. Your taste buds—and your waistline—will thank you!