Enjoy the rich, savory flavors of a classic dish without all the carbs!
I used to love ordering French onion soup in restaurants. It comes to the table with that lovely topping of browned, bubbly cheese melting down the sides of the dish. Then there’s a little cube of bread waiting inside the soup like a secret prize, soaking up the oniony, savory goodness! Besides, onions have long been one of my favorite vegetables. That might sound weird, but I love their savory-sweet flavor and fresh, juicy crunch. My dad and I used to munch on raw scallions dipped in table salt while we waited for mom to finish cooking dinner.
When my partner and I decided to try a low-carb diet, I was relieved that onions could still be on the table for me. Yes, I need to practice moderation with them to stay within keto guidelines—but that’s better than them being taboo!
And I was really happy when I discovered this keto French onion soup recipe. I’d never made French onion soup from scratch before. Our one-month anniversary of going low-carb was the perfect occasion. I found the soup itself pretty simple to prepare, as it’s similar to other recipes I’ve made. The chaffles though, were a little bit of a challenge. I borrowed my sister’s mini waffle maker—then burned my entire first batch. Sigh. I finally got the hang of it with the second batch, keeping my nose attentive to the slightest aroma of doneness and maintaining a watchful eye on the machine’s indicator light. That batch was amazing! Golden brown, crispy, and mouthwateringly aromatic.
In combination with the deeply savory soup, those cheesy little waffles were like icing on a cake. They added just enough tang and crunch to complement the sharpness of the Gruyère and the richness of the soup. I’m sure we’ll make this recipe fairly often, now that I’m more confident with it. You won’t believe how much it takes like the traditional dish—sans all those extra carbs!
What are chaffles?
The word chaffle is a mashup of the words cheese and waffle. They’re a remarkably recent addition to the modern low-carb kitchen that emerged as both an online sensation and a practical workaround for keto dieters missing bread and baked treats.
The chaffle is essentially a waffle made from just eggs and cheese, with many variations introducing almond or coconut flour for texture. Though their name is playful, chaffles fulfill serious roles—playing the part of sandwich bread, burger bun, and even pizza crust or taco shell. Their versatility, ease, and minimal ingredients made them a runaway hit in the keto and gluten-free community, especially after going viral on TikTok and in online recipe groups around 2019 and 2020. You likely remember your social media feeds brimming with imaginative savory and sweet spins on chaffles, as people experimented with everything from pumpkin spice to brownies.
The exact origin of the chaffle is fuzzy. No single person or company gets credit for the craze—rather, it’s emblematic of how online food culture can spark totally new traditions in just a few years. I love how simple and adaptable they are, as well as the crispy, savory flavor of the cheesy chaffles in this recipe. To me, the chaffle represents how dietary necessity and creativity can yield something truly novel.
How do I store leftovers?
The best plan is to store your leftover French onion soup and chaffles separately. Let the soup cool completely, then transfer it to an airtight container or bag. It’ll keep in the fridge for up to 5 days or in the freezer for up to 3 months. Store completely cooled chaffles in an airtight container or bag in the fridge for up to 3 days or in the freezer for up to 2 months. Thaw frozen soup in the fridge overnight, then reheat on the stovetop or in the microwave. Revive your chaffles in a toaster, air fryer, or oven at 350°F for 3–5 minutes, until crisp. Then you can assemble bowls of soup topped with chaffles and freshly grated Gruyère, broil, and serve.
If your leftovers are fully assembled portions topped with chaffles and broiled cheese, you can still save them! Just know that the chaffles will get softer as they soak up more liquid, and the broiled cheese will lose its crispiness. Cover each portion tightly with plastic wrap and store them in the fridge for up to 2 days. I do not recommend freezing them, as they will not be as appealing after thawing.
Similar recipes to try
Looking for more low-carb soup recipes to try? Check out this one for Healthy Roasted Tomato Basil Soup, this Healthy Cabbage Soup recipe, this hearty Instant Pot Keto Sausage Soup, and this Low-Carb Vegetable Beef Soup recipe that’s also paleo-friendly and Whole30-compliant.
Keto French Onion Soup Recipe
Ingredients
- 5 tablespoons butter
- 2 large onions sliced
- 2 teaspoons garlic minced
- 1/3 cup white wine
- 6 cups beef stock
- 1 bay leaf
- 2 sprigs thyme
- 3/4 cup mozzarella cheese shredded
- 3/4 cup cheddar cheese shredded
- 3 eggs
- 6 ounces Gruyère cheese shredded
Instructions
- Add the butter to a large pot over medium heat. Add the onions and sauté, stirring frequently, until they're caramelized, about 20-30 minutes.
- Add the garlic and cook for another 1 minute. Pour in the wine and let it simmer for 2 minutes.
- Stir in the beef stock, bay leaf, and thyme. Simmer for about 10-15 minutes.
- While the soup is cooking, make your chaffles. Mix the mozzarella, cheddar, and eggs in a bowl. Spoon out enough batter to just fill a mini waffle maker. Cook until the chaffle is golden brown and the waffle maker's indicator light goes off or steam stops, typically about 3-4 minutes. Repeat with the remaining batter, which should make about 6 small chaffles.
- Fish out the bay leaf and thyme from the soup and discard them. Ladle your soup into oven-safe dishes. Place a chaffle on top of each, then sprinkle some shredded Gruyère cheese on top of that. Broil until the cheese is melted, about 2-3 minutes.
- Serve immediately.
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