This keto French onion soup is a cozy and comforting appetizer that takes just 10 minutes to make! No flour or thickeners needed, it’s topped with toasted low carb bread with plenty of melted gruyere on top!
Keto French Onion Soup
The creme de la creme of all soups though would have to be French onion soup. If there is one soup that could convert a soup hater, it would have to be this one.
Is French onion soup keto?
Traditional French onion soups are not keto friendly, as they use a combination of flour and starch to thicken it, along with a plethora of onions. Luckily, with a few tweaks (and some deliciously toasted keto bread!), you can enjoy this soup on ANY diet you may or may not follow.
Now, besides myself, none of my housemates follows a low carb diet but this is easily one of my most requested dishes to make when we host friends over. One of my housemates is actually from France and he claims this tastes exactly like the kind of soup he’d enjoy at restaurants there.
Why this keto French onion soup recipe will leave you begging for a second bowl-
- No flour or thickeners. Unlike traditional soups, this one does NOT need any flour to thicken it up.
- 5 ingredients. The soup itself needs just 5 main ingredients to make. I dare you to find an easier (and just as delicious!) soup out there.
- Topped with toasted cheesy bread that is keto friendly. The best part of any French onion soup is the cheesy croutons on top, and we’ve included that too…in a keto friendly way.
- Ridiculously quick and simple. Set your timers to 20 minutes because that is all it’ll take to whip this up.
What I love about this recipe is that it looks and sounds incredibly fancy but is one of the EASIEST soups you’ll ever make. This is the kind of dish you’ll make to impress your friends!
What you’ll need to make this recipe
For the soup
- Butter– Unsalted butter is preferred, as there is already salt in several of the other ingredients.
- Onions– White onion is preferred but yellow or sweet onions can also be used. Finely slice your onions to the cook quicker.
- Granulated sweetener of choice– Just a pinch to balance out the salty flavors.
- Salt and pepper– To taste.
- Beef broth– I prefer using broth that has been premade instead of bouillon cubes,
- Worcesteshire sauce– Adds a lovely complex flavor and an enhances the meaty flavors.
For the toasted cheesy bread
- Keto buns– Traditional French onion soups typically use sliced baguette. To replicate this, we’ve used thinly sliced keto hot dog buns. You can also use thickly sliced keto bread or even keto rolls.
- Gruyere cheese– A perfectly rich and creamy cheese that MUST be paired with French onion soup! Always use freshly grated cheese has it has a better flavor and melts much easier.
- Fresh thyme– To serve.
How do you make keto French onion soup?
Start by adding butter to a deep pot or Dutch oven and placing it over medium heat. Once melted, add the onions and sweetener and sautee until tender. Add the beef broth and Worcestershire sauce and bring it to a simmer. Once it starts simmering, cover the pot and allow it to simmer for a further 10 minutes. Keep the soup warm while you prepare the cheesy croutons.
To make the cheesy croutons, slice your keto hot dog buns or keto bread into 2-3 inch slices. Have each slice then place them on a baking sheet. Sprinkle each piece of bread with freshly grated Gruyere cheese and bake in a preheated oven until the cheese has melted and the bread is crispy around the edges.
Finally, ladle out the soup into small bowls and top with the cheesy toasts.
Tips to make the best recipe
- Do not cut the onions too thinly or they will caramelize too quickly then shrivle up by the time the soup is cooked.
- Use a good quality beef broth as the flavor really makes a difference.
- Always shred your cheese by hand- It not only tastes better but it also melts much more beautifully.
- If you’d prefer to have cheesy croutons, slice your bread into quarters instead of halves.
Storing, freezing, reheating and make ahead instructions
These tips refer to the soup and NOT the cheesy croutons. Always make the croutons fresh.
- To store: Leftover soup can be stored in the refrigerator, covered, for up to 1 week.
- To freeze: Place the cooled soup in an airtight container and store it in the freezer for up to 6 months.
- Reheating: Either microwave the soup in 30-second spurts or reheat in a saucepan.
- To make ahead: For optimum freshness, soup can be prepared up to 3 days in advance and stored in the refrigerator. When ready to serve, bring it to room temperature then place it over medium heat until hot. While the soup is heating up, prepare the cheesy croutons.
What to serve with French onion soup
Because this soup already has a ‘bread’ element built into it, it can be a meal in itself. However, you can make smaller portions and use them as an appetizer or side dish to some protein-heavy entrees. Some of my favorite recipes to pair it with include crack chicken, grilled chicken, stuffed peppers, and a classic meatloaf.
More keto soup recipes to try
Frequently Asked Questions
Onions are a suitable vegetable to include on a keto diet, provided they aren’t eaten in excess. Per 1 cup of raw sliced onions, there are 9 grams of net carbs.
The main difference between a classic onion soup and an authentic French onion soup is that the latter always uses beef stock or beef broth. A generic onion soup often uses vegetable broth or sometimes chicken broth.
Depending on which recipe you make, French onion soup can be very calorie dense. In this version, each serving contains a mere 265 calories including the cheesy toast.
Keto French Onion Soup
- 1 ounce butter
- 4 large onions thinly sliced
- 1/2 teaspoon erythritol or any granulated sweetener
- 1/2 teaspoon pepper
- 32 ounces beef broth
- 3 tablespoons Worcestershire sauce
For the cheesy toasts/croutons
- 2 keto hot dog buns * See notes
- 1 1/2 cups Gruyere cheese finely shredded
- 4 springs Thyme loosely torn
- Preheat the oven to 200C/400F. Line a large baking sheet with parchment paper and set aside.
- Place a large soup pot over medium heat. Once hot, add the butter to melt. Add the sliced onions, sweetener, and pepper and saute for 8-10 minutes, until tender.
- Add the beef broth and Worcestershire sauce and bring to a simmer. Once it starts simmering, cover the pot and let it simmer for a further 10 minutes.
- While the soup is simmering, prepare the cheesy toasts. Slice your two keto hot dog buns into 6 thick slices and slice each one in half. Place the twelve pieces of bread onto the lined sheet. Sprinkle half the Gruyere cheese over the top. Bake in the oven for 6-8 minutes, until golden brown.
- Ladle the soup into small bowls. Add 1-2 pieces of the cheesy toast on top of each soup bowl and sprinkle with extra Gruyere cheese and a sprig of thyme.