This Bistro French Onion Soup combines deeply caramelized onions and leeks with rich beef broth, white wine, sherry and fresh thyme. Each bowl is finished with oversized French bread croutons and melted Gruyère for the kind of cozy, deeply savory soup you would expect from a classic French bistro.
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A classic, cozy soup reminiscent of sitting in a French bistro. Oversized seasoned croutons lend to a perfect bite with a delicious Gruyere cheese pull and hints of fresh thyme. This is the ultimate comfort food and it’s a must have for cold winter nights. This recipe makes enough for six large bowls and freezes well.
Caramelize the Onions
Properly caramelized onions take time, plan on a little over an hour to reach the desired texture and flavor. I like to use six large Walla Walla Sweet onions together with a couple large leeks. It seems like a lot of onions, as they fill the large soup pot, but after over an hour of caramelizing, they reduce down to just about one quarter. The process is absolutely necessary to obtain the nice, sweet flavor that comes from caramelization. The photos below show the technique in fifteen minute increments.
I like to start with about six tablespoons of butter and two tablespoons of bacon grease. The bacon grease just adds a deeper flavor, but isn’t necessary. I save my bacon grease and always have on hand for using when I cook. If you don’t have any bacon grease, not a problem, just use a full stick of butter instead of the six tablespoons. Melt the butter/bacon grease over medium heat, add the sliced onions and leeks, a good size pinch of salt, then let the caramelization begin. You will want to stir often and keep an eye on the onions. If they start to brown too quickly, just reduce the temperature and continue slowly caramelizing.
Why You’ll Love Bistro French Onion Soup
- Deep flavor from slowly caramelized onions and leeks
- Rich broth enhanced with white wine, sherry and thyme
- Oversized homemade French croutons
- Finished with bubbling melted Gruyere
- Freezer-friendly and makes six generous servings
What You’ll Need for Bistro French Onion Soup
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- Onions – Six large Walla Walla Sweet onions or your favorite yellow onions.
- Leeks – Two large leeks add depth of flavor.
- Beef Broth – Better Than Bouillon Roasted Beef, made extra strong.
- White Wine – I keep a bottle of basic, inexpensive white wine on hand.
- Sherry – Cooking sherry adds that French onion soup flavor we love.
- Thyme – Fresh sprigs of thyme.
- Other – Butter, flour, bacon grease, salt and pepper.
Make It Your Way
Walla Walla sweet onions can be replaced with yellow or Vidalia onions.
Can’t find Gruyere? Use Swiss, Comte or provolone cheese.
Replace the bacon grease with additional butter.
Use dry sherry in place of cooking sherry.
Bistro French Onion Soup
Equipment
- 6 Oven safe soup bowls
Ingredients
- 6 large Walla Walla Sweet onions sliced in 1/4 inch rounds
- 2 large leeks sliced in 1/4 inch rounds
- 1/2 cup butter
- 1 tsp. salt
- 1 cup white wine
- 1/2 cup sherry cooking wine
- 1 tbsp. bacon grease can sub cooking oil / butter
- 2 heaping tsp. flour
- 8 cups water
- 12 heaping tsp. Better Than Bouillon – Roasted Beef
- 3 sprigs fresh thyme
- salt and pepper to taste
Croutons
- 6 1 inch thick French bread slices
- 1/4 cup olive oil
- 1/2 tsp. salt
- 1/4 tsp. pepper
- 2 sprigs thyme stems removed
- 12 slices Gruyere or Swiss cheese 2 slices per bowl
Instructions
- Caramelize the onions and leeks over medium-low heat: Melt butter in large stock pot over medium low heat, add onions, leeks and salt. Slowly cook the onion mixture down, stirring occasionally until fully caramelized. This process should take 90 minutes.
- Add wine and sherry to the pot, cook for about 2 minutes. Stir in bacon grease and flour until combined well, cooking an additional 2 minutes. Add water, bouillon, thyme, salt and pepper. Simmer on medium low while you make the croutons.
- Spoon soup into oven safe bowls, place a few croutons on top, cover with two slices of Gruyere or Swiss cheese. Broil until melted.
Croutons
- Cut thick sliced French bread into large oversized cubes. Toss in a mixing bowl with olive oil, salt and pepper. Place cubes in a medium sized pan over medium high heat and brown on each side. Remove from heat and sprinkle thyme leaves over croutons.
SALTY OWL TIP
TIP for PERFECTLY CARAMELIZED ONIONS: Keep the heat at medium-low and give the onions plenty of time to soften and develop their deep golden color. Stir periodically, scraping up any browned bits from the bottom of the pot. If the onions begin browning too quickly or sticking, reduce the heat and add a small splash of water. Don’t rush this step—the caramelized onions create the soup’s signature flavor.
More Seriously Good Recipes
If you’re craving more cozy, cold-weather comfort food, try my Black-Eyed Pea Soup with smoky ham and tender collard greens. For a rich, slow-cooked dinner, Red Wine Braised Short Ribs are fall-apart tender with mushrooms and herbs served over creamy polenta. And if you need an elegant side dish, Fennel Gratin for Two layers creamy yellow potatoes with mild fennel and sharp white cheddar.
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