French onion soup is a classic dish renowned for its rich flavor and comforting warmth. This article provides a comprehensive guide to making a keto-friendly version of this beloved soup, offering a culinary hug in a bowl without compromising your low-carb lifestyle.
Is French Onion Soup Keto-Friendly?
Typically, French onion soup is not keto-friendly due to the high carbohydrate content of onions, bread, and sometimes wine. However, with a few modifications, it can be transformed into a delicious and satisfying keto meal. This keto French onion soup minimizes carbs while retaining the classic flavors you love. By using fewer onions, skipping added sugar, and opting for low-carb bread or chaffles, you can enjoy a generous portion of this soup while staying within your daily carb limit.
Key Ingredients and Substitutions
Onions
Yellow onions are traditionally used for French onion soup, providing a mellow flavor when caramelized. White or red onions can also be used with minimal impact on the final result. Be sure to slice the onions at least ⅛" thick to prevent them from shriveling during cooking.
Broth
Traditionally, beef broth is used to give French onion soup its rich flavor. However, chicken broth can be substituted for a lighter flavor. For a vegetarian or vegan option, vegetable broth or stock can be used, but be aware that the carb content may be slightly higher.
Cheese
Classic French onion soup is typically topped with a French cheese like Comte, Gruyere, or Swiss. If these are unavailable, a mild cheese like mozzarella or muenster can be used. Cheddar cheese can also be used, but its strong flavor may compete with the soup's other flavors. Gruyere cheese is a popular choice for its meltiness and nutty flavor.
Read also: Easy Low-Carb Cheese Crackers
Bread
Traditional French onion soup uses sliced baguette. For a keto-friendly alternative, use keto bread, sourdough chaffles, or keto cheese breadsticks.
Other Ingredients
- Butter: Adds richness and flavor to the soup, essential for caramelizing the onions. If you need to make this dish dairy-free, use avocado oil.
- Garlic: Enhances the savory flavor of the soup.
- Thyme: Adds an earthy, aromatic note to the soup.
- Bay Leaf: Infuses the soup with a subtle, herbal flavor.
- Worcestershire Sauce: Contributes umami and depth of flavor. For a plant-based alternative, use coconut aminos.
- Red Wine/Dry Sherry: Adds complexity and acidity to the soup.
- Arrowroot/Cassava Flour/Tapioca Starch: Used as a thickening agent.
- Salt and Pepper: To taste, enhancing the overall flavor profile.
- Granulated Sweetener: Just a pinch to balance out the salty flavors.
Step-by-Step Instructions
Caramelizing the Onions
- Melt butter (or avocado oil for dairy-free) in a large skillet, Dutch oven, or cast iron pot over medium heat. Use about 4 tbsp of butter.
- Add thinly sliced onions (about 3 pounds) and salt (¾ tsp) and cover, letting the onions soften for 5 minutes.
- Remove the lid and let the onions caramelize until golden brown over medium heat, stirring occasionally. This process may take 45 to 60 minutes. Adjust the heat if the onions are browning too quickly. Patience is key to achieving the perfect caramelization. You want them to be a dark golden brown but not burned.
Building the Soup
- Warm the beef bone broth (2 quarts) in a saucepan over low heat.
- Once the onions are caramelized, deglaze the pot with red wine or dry sherry (1 cup) and allow the mixture to come to a boil. Alternatively, deglaze the pan with 1/2 cup of the beef or chicken broth. Scrape all the browned bits from the bottom of the pot.
- Stir in arrowroot, cassava flour, or tapioca starch (1 tbsp) and let it thicken for a minute or two.
- Slowly add the warm bone broth, remaining salt (¼ tsp), pepper (½ tsp), thyme, and bay leaf to the onion mixture and boil uncovered for 10 minutes.
- Remove the sprigs of thyme and bay leaves and season the soup with additional salt and pepper to taste.
Preparing the Cheesy Topper
- Preheat the oven broiler.
- Slice keto bread (8-12 slices, ½ inch thick) or prepare chaffles.
- Arrange individual ovenproof ramekins on a baking sheet.
- Ladle soup into the ramekins and cover the soup with bread slices or chaffles.
- Sprinkle each dish generously with grated Gruyère or your cheese of choice (about 1/4 cup per bowl).
- Watching closely, broil for a minute or two until the cheese melts and browns.
Alternative Cooking Methods
Slow Cooker
For those who prefer a hands-off approach, French onion soup can be made in a slow cooker. Add all the ingredients (except the cheese) to the slow cooker and cook on low for 6-8 hours or high for 3-4 hours.
Instant Pot
The Instant Pot offers a quicker alternative. Set the Instant Pot to the high saute setting, add butter/oil, and cook the onion until tender, about 3-5 minutes. Add garlic and cook for an additional minute. Pour in broth and deglaze the bottom of the pressure cooker. Stir in salt, pepper, and thyme. Close the lid and seal the valve. Cook on high pressure for a specified time (consult your Instant Pot manual), then follow the instructions for releasing the pressure.
Serving and Storage
Ladle the soup into bowls and top with the cheesy bread or chaffles. Serve immediately and enjoy the rich, comforting flavors.
To store, thoroughly chill the soup and refrigerate it in an airtight container for up to 5 days. The soup can also be frozen for longer storage. My favorite way to freeze saucy and soupy recipes is by using Souper Cubes! These amazing freezer-safe cubes are perfect for freezing portions of all my favorite soups, stews, and other saucy meals. I freeze them then pop them out and put the rectangular frozen blocks into a zipper-top freezer bag. It makes storing them SOOOO much easier!
Read also: Keto Calorie Counting: A Detailed Guide
Tips and Tricks
- Don't cut the onions too thin. Otherwise, you risk them cooking too quickly and shriveling up by the time the soup is cooked.
- Patience is key when caramelizing the onions. Low heat and lots of time will do the trick.
- For a richer flavor, use homemade beef stock.
- To prevent xanthan gum from clumping, sprinkle it over the top when adding and whisk well.
- If you want to make the soup ahead of time, prepare it up to three days in advance and store it in the fridge. Before serving, warm it on the stove over medium-low heat, then serve with the cheesy croutons.
Nutritional Information
Please note that the nutritional values for this recipe do not include a chaffle or low-carb bread for topping your soup. The nutritional information provided is an approximate value based on available online ingredient information and cannot be guaranteed. Erythritol carbs (sugar substitutes) are not included in the carbohydrate counts as they have been shown not to impact blood sugar, and they have zero calories and zero carbs.
Other Keto Soup Recipes to Try
- Keto Mushroom Soup
- Keto Cauliflower Soup
- Keto Broccoli Cheese Soup
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