French Lentil Soup

Name: French Lentil Soup
Prep time: 10 min
Cook time: 1 h 30 min
Total time: 1 h 40 min
Yield: 8
Cuisine: Healthy
Ingredients: 2 tablespoons extra-virgin olive oil; 1 tablespoon butter; 4 cups onion, thinly sliced (about 2 sweet onions and 2 red onions); 1-2 garlic cloves, peeled and minced; 1-2 tablespoons Worcestershire (optional); 12 cups vegetable broth (or chicken broth); 1 cup dried green lentils; 1 bay leaf; 1 sprig fresh thyme; 2-3 sprigs parsley; 1/2 cup parsley, chopped (for garnish); Baguette slices; Olive oil; Parmesan cheese or Gruyere cheese

by Deborah on Nov 30, 2020 (updated Nov 22, 2023) 0 comments

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Vegetarian French onion soup meets lentil soup with this delicious French Lentil Soup recipe. This is the best lentil soup with all the flavors we love about French onion soup with added green lentils (or brown lentils) for a more substantially filling and protein rich vegetarian soup.

This vegetarian lentil soup makes a hearty main or you can serve it as a starter. If you’re like me and love good healthy soup recipes, especially during chilly winter months, I know you’ll enjoy this French Lentil Soup recipe as much as I do!

If you’re wanting to add more meatless meals to your diet, lentils is a great place to start.

Best French Lentil Soup Recipe

This is the best lentil soup recipe! We use many of the same ingredients that you’d use to make a vegetarian French onion soup, then add in some green lentils. It’s a warm and cozy bowl of delicious!

Lentils – We use either green lentils or brown lentils for this soup because they tend to hold their shape.
Aromatics – we use a delicious combination of sweet onion, red onion, garlic, fresh parsley, thyme and dried bay leaves)
Butter – We use a combination of butter and extra-virgin olive oil to saute the onion with.
Broth – You can use either vegetable or chicken broth for this soup.
Worchestershire sauce – A little Worchestershire sauce give this soup a little French Onion Soup flavor.
Cheese Toasties – We garnish this soup with cheese toasties made with French bread, olive oil and Parmesan cheese.

Find the printable recipe with measurements below.

Variations

Wine – Pour in 1/2 cup sherry or wine (red or white) to deglaze the onions
Cheese – Garnish with Gruyere cheese instead of Parmesan

How to Make French Lentil Soup

This French lentil soup recipe starts out as a vegetarian French onion soup with lots of caramelized onions then we add in the lentils. This combo makes the best lentil soup recipe!

Caramelize onions. Melt butter in a large soup pot or Dutch oven over medium low heat. Add onions, sprinkle with a pinch of salt, and cook for 40 minutes until onions are soft and caramelized. Add garlic the last 2-3 minutes of cooking.
Add broth and herbs. Pour in broth, lentils, bay leaf and sprigs of thyme and parsley.
Simmer. Bring to a boil, then place lid on pot and reduce heat to a low simmer for 40-45 minutes until lentils are tender.
Make toasties. Arrange baguette slices brushed with olive oil on a baking sheet in a single layer. Bake for 1-2 minutes then remove from oven and sprinkle with grated Parmesan cheese and bake another 2-3 minutes until melted.
Serve. Ladle soup in bowls and float 2-3 Parmesan toasties on top.

Best Onions for French Onion Soup

The best onions to use for French onion soup are yellow onion, sweet onion (such as Vidalia and Walla Walla) and red onion.

Yellow onion. Yellow onions are probably the most commonly used onion. They’re great grilled or simmered in soups and stews.
Sweet onions. Sweet onions (Vidalia and Walla Walla) have a little less of a bite to them than the yellow or white onion, and they taste a little on the sweet side.
Red onions. Red onions are similar in flavor to the rustic yellow onion.

How to Caramelize Onions

This is probably the most important part of a good onion soup. Caramelizing 3-4 onions can typically take up to an hour, but we cut down on time just a bit for this soup and we caramelize the onions for about 40 minutes.

Slice onions. Trim the tip and root from onions. Cut the onions in half and remove the skins. Cut each half into thin slices.
Heat butter. Melt butter in large skillet over medium low heat. Or if using olive oil, heat oil over medium low heat.
Add sliced onions. Add all of the sliced onions to the pan and stir them to coat with melted butter or olive oil.
Cook. Cook the onions and check every 5-7 minutes. As the onions cook, stir and scrape any onion glaze (fond) that forms at the bottom of the pan. As the onions start to soften, there will be liquid in the pan. After about 20 minutes, the onions will turn blonde and become sticky and you’ll see some of the glaze (fond) building up at the bottom of the pan. Towards the end of the process, the onions will turn a darker brown color and release a delicious aroma.

Tips for Caramelizing Onions

The best pans for caramelizing onions is a good stainless steel or cast iron skillet. You can use a non-stick pan, but the onions just don’t caramelize quite as nicely.
Caramelizing onions is a process that breaks down the sugars in the onions giving the onions a deep rich flavor. It’s really as simple as melting some butter (you can also use vegan butter or olive oil) and adding the thinly sliced onions to the pan along with a pinch of salt.
Don’t over-crowd the pan. Depending on the size of your pan, it’s best to caramelize 3-4 onions at a time.
Cook the onions slowly on low heat until they turn a rich mahogany brown in color.
Once the onions start to cook, be sure to check on them every 5 – 7 minutes to stir them. Scrape the sticky glaze (fond) that builds up on the bottom of the pan and stir it into the onions. Lots of flavor in the fond!
The onions will start to dry at the end of the caramelization process. You can deglaze the pan with either water, broth, sherry or wine.

What Cheese Goes on French Onion Soup

Classic onion soup is traditionally topped with crusty bread and sliced or shredded Gruyere cheese. I’ve kept things simple (and lower in calories and fat) by garnishing this soup with Parmesan cheese, but feel free to go with Gruyere cheese or no cheese at all if you like.

What Are the Best Lentils to Use

There’s a variety of different types of lentils to cook with, such as green lentils (also called French lentils or Le Puy lentils), red lentils, black lentils (also called beluga lentils) and brown lentils. I find that Le Puy lentils (also called French Green Lentils) or just plain green lentils and brown lentils are the best lentils to use when making lentil soup with because they tend to hold their shape better and retain a slightly firmer texture. They take about 40-45 minutes to cook cook.

Serving Suggestions

This French Lentil Soup is substantially filling on its own, but you could easily serve it with warm crusty bread, a light salad or as a starter soup.

Looking for Lentil Soup Recipes to Make?

More Vegetarian Soup Recipes

Still want more ideas? Check out all my healthy soup recipes.

Yield: 8 servings