Low-Carb French Onion Soup

French onion soup is a beloved comfort food classic, and this rich, caramelized onion soup version takes it to the next level. Served over chunks of bread topped with melted cheddar, it's traditionally a carb-heavy dish. Our version, however, is a delightful low-carb alternative that still captures that indulgent comfort food essence.

For the cheesy toasts, I've opted for Sourdough Keto Baguettes recipe to keep it keto and gluten-free, but feel free to use any keto bread you prefer. The cheese is melted onto the toasts before adding them to the soup, ensuring they stay crisp and don’t get soggy too quickly.

Preparation time

Hands-on:    20 minutes
Overall:     1 hour 20 minutes

Nutritional values (per serving, about 1 ¹/₃ cups/ 320 ml, with 2 slices of cheesy toast)

Total Carbs	16.6	grams
Fiber	7.9	grams
Net Carbs	8.8	grams

Protein	17.1	grams
Fat	26.8	grams
of which Saturated	11	grams

Energy	373	kcal

Magnesium	166	mg (42% RDA)
Potassium	664	mg (33% EMR)

Macronutrient ratio: Calories from carbs (10%), protein (20%), fat (70%)

Ingredients (makes 6 servings)

Cheesy Keto Toasts:

1 recipe Sourdough Keto Baguettes recipe (you will only need half)
1 cup grated Gruyere cheese or cheddar cheese (113 g/ 4 oz)

Soup:

4 tbsp unsalted butter or ghee (60 ml)
3 large brown onions, sliced (450 g/ 1 lb)
1 bay leaf
¹/₂ cup dry white wine (120 ml/ 4 fl oz)
4 cups beef stock (960 ml/ 32 fl oz)
3 cups water (700 ml/ 24 fl oz)
thin strips of peel from ¹/₂ organic lemon
1 tbsp Dijon mustard (15 ml)
1 tsp salt, or to taste
black pepper, to taste

Instructions

Preheat oven to 200 °C/ 400 °F (conventional), or 180 °C/ 355 °F (fan assisted). To make the toast, follow directions here but instead make one large baguette. Allow baguette to cool completely while you make the soup.
Note: You will only be using one large baguette, and need only half of the mixture, so you can either use half of the ingredients to make one large baguette, or make the whole recipe and use the remainder to eat as per usual.
Heat the butter in a large saucepan over low-to-medium heat. Thinly slice the onions and add to the pan. Reduce heat to low and cook, stirring every few minutes, for 30 mins or until onions have softened and starting to brown.
Increase heat to medium high, add 1 tsp salt and cook, stirring frequently, around 10 minutes until caramalized.
Reduce the heat slightly, add the wine and simmer, stirring, until the wine is nearly evaporated, around 2 minutes. Add the bay leaf, lemon peel and season with 1 tsp salt.
Add the stock, water, and reduce heat to low, cover and simmer gently for 20 mins or until flavors develop. Whisk in mustard. Add salt and pepper to taste.
To make the cheesy toast, slice the baguette into about ¹/₂ inch (1 ¹/₄ cm) slices. Layer on a baking tray and place under a grill/broiler. Cook until golden brown and then remove.
Flip over, top with grated cheese, and return to the broiler.
Serve with cheesy toast and soup. Serve immediately while still hot. To store the soup (without the toast), let it cool down and keep in the fridge for up to 5 days, or freeze for up to 3 months. The toast should always be make fresh.