Slowly caramelizing onions in butter until they're golden brown makes the perfect base for homemade French Onion Soup. Beef stock and white wine provide rich flavor, and sherry adds depth and a touch more sweetness to the soup. It's a great project for a lazy afternoon, and dinner will be delicious!
[November, 2022: I've reworked the recipe and updated this post with all new pictures. Enjoy!]
Why this recipe works
- Slowly caramelizing the onions brings out their sweetness
- Beef stock and white wine bring body and a touch of acidity, while sherry adds more sweetness and complexity
- A topping of garlic-rubbed toast and melted Gruyére cheese adds substance and gooey goodness!
French Onion Soup is one of those easy, non-fussy recipes, but it's not to be rushed. Slowly cooking thinly sliced onions in butter allows them to melt into a pile of soft, golden-brown, caramelized threads. With all the sulfur cooked out, the onions' sweetness shines through. And besides slicing the onions, there's very little hands on work to do.
After hours of waiting and caramelizing the onions, the soup itself comes together relatively quickly, again with just a little work on your part. Using tools like a mandolin slicer to slice the onions and a chef's torch makes the work quick and fun.
This recipe is a great project for a lazy afternoon, and dinner will be delicious!
By the way, if you want another use for the chef's torch, you can make a foolproof Slow Cooker Crème Brûlée while the onions are cooking down. Low and slow heat is ideal for baking custard gently. Then adding a crunchy sugar crust makes for a fun dessert!
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What you need
At its most basic, French Onion Soup ingredients are simple: onions (yellow or sweet), butter, beef stock, salt, and pepper. White wine adds a touch of acidity while loosening up the cooked-on onion bits (and the alcohol is cooked off). Simmering the soup with beef stock (or beef broth), thyme, and bay leaves provides a richer flavor than just water.
Finishing the soup with sherry adds depth and a touch more sweetness to the soup, but since the alcohol isn't cooked off here, it's use is optional and for adults-only. You wouldn't want add the sherry if you want a non-alcoholic onion soup, like when serving kids or pregnant women.
The combination of garlic-rubbed toasted baguette slices and and gooey melted Gruyére cheese adds substance to the overall dish.
Speaking of the thyme and bay leaves, keep the soup free of floating leaves by tying the thyme and bay leaves into a bundle (aka bouquet garni). Lay out the bay leaves, one on top of the other, then fold the thyme stems to fit on top lengthwise. Roll the bay leaves to enclose the thyme and wrap the bundle with kitchen twine. It will be easier to fish it out of the soup when it's done.
How to make French Onion Soup
Plan to set aside an afternoon to make the recipe because you want to caramelize the onions low and slow (cold, rainy Sundays are designed for this type of cooking).
Step 1: Slice the onions
Cut the onions in half from the top to the root. Thinly slice the onions using a mandolin slicer, sliding the onion across the blade sideways, that is, the narrow part facing forward (photo 1). Be sure to use the finger guard to protect your fingers.
If you don't have a mandolin, slice the onions thinly with a chef's knife.
Step 2: Caramelize the onions
Melt 3 tablespoons of butter over medium heat in an 6-quart enameled cast-iron pot (or another large heavy pot with a lid). Add the onions, sprinkle them with 2 teaspoons of salt, then cover and cook until the onions have heated through and started to steam, about 10 minutes (photo 2).
Uncover the pot, stir in the black pepper, then reduce the heat to low and cook, stirring occasionally, until the onions have caramelized, about 3 hours (photo 3).
Step 3: Make the soup
When the onions have completely cooked down, (the liquid has evaporated, and the onions have turned amber), add the wine and raise heat to high. Cook until almost all liquid has evaporated, about 15 minutes (photo 4).
Add the stock, water, and the bouquet garni to the pot with the onions. Bring to a boil (this can take about 15 minutes). Reduce to a simmer and cook, uncovered, until the soup has thickened, 20 to 30 minutes.
Remove the pot from heat, remove the bundle, and whisk in the remaining 2 tablespoons of butter (photo 5). Taste and adjust the seasoning as needed. If desired, you can add ½ to 1 teaspoon of sugar if the soup isn’t sweet enough.
Step 4: Prepare the bread slices
Cut two ½-inch slices of the baguette for every serving of soup (make sure they will fit in the ramekins). Lightly toast the slices in the toaster until they are crisp and dry but not browned. Alternatively, preheat the oven broiler and place the bread slices on a half sheet baking pan. Broil the slices, about 1 minute per side.
Rub one side of each toast with the garlic clove and set aside.
Step 5: Assemble the soup
Add ½ teaspoon of sherry (if using) to the bottom of four 16-ounce oven-safe ramekins. Top each serving of soup with the two garlic-rubbed toasts. Divide the cheese among the servings, covering the bread and some of the soup (photo 6).
Carefully broil the tops of the soup with a chef's torch until cheese is melted and bubbling. If you don't have a torch, place the ramekins on the half sheet baking pan and transfer to oven to broil and melt the cheese, about 4 to 8 minutes (photo 7).
If you don't have oven-safe ramekins, then top each garlic-rubbed toast with some cheese and melt in the broiler prior to putting them on the soup, about 2 minutes. Divide the sherry and soup among the bowls, sprinkle with the remaining cheese, and top each serving with two cheese toasts.
Questions asked and answered
Here are some questions you might have...
While you can use yellow, white, or even red onions for French Onion Soup, sweet onions (Vidalia or Walla Walla) don't have the same astringent qualities the others have. When caramelized, they lend their inherent sweetness to the soup so that adding sugar may not even be necessary.
While similar, beef stock and beef broth have one important difference: beef stock doesn't contain salt.
Beef stock (sometimes called bone stock or bone broth) is made from slowly simmering beef bones (usually roasted, sometimes including tomato paste) with a vegetable mix of onions, celery, carrots and an assortment of herbs and spices, including parsley, bay leaves, thyme, and black peppercorns. After the liquid is chilled and skimmed of fat, you have a liquid ingredient with a rich flavor and thick mouthfeel that's perfect for adding flavor to soups and stews.
Beef broth can be made from meat rather than beef bones along with the vegetables, salt, herbs, and spices. The flavor isn't as rich as stock, but broth can be used as a stand-alone soup rather than just as an ingredient.
Traditionally, French Onion Soup (Soupe à l'Oignon Gratinée), was a simple peasant dish made with well-caramelized onions simmered with water and topped with day-old bread and melted cheese. While that version has clean onion flavor, using beef stock and white wine adds a depth of flavor that complements and enhances the richly sweet cooked onions.
Beef broth is beef stock that's salted to taste. If you use broth instead of stock in this French Onion Soup recipe, make sure to adjust the amount of salt to compensate.
You can make French Onion Soup without wine. Just replace the wine with more beef stock to deglaze the pan (to loosen up the brown bits from the pan), then adjust the taste of the soup later with a bit lemon juice (to add acidity).
Pro Tip: Use a mandolin to slice the onions, cautiously
Yes, I cry whenever I slice onions, but using a mandolin slicer lets me get the job done quickly and evenly. And yes, it's very important to use the finger guard - you want to keep your fingers away from that sharp blade!
Onions at their best
There's so much to love about a well-made French Onion Soup recipe. There's the rich flavorful broth with a complex sweet and butter body, soft and supple caramelized onions, the toasty bread chewiness, and the ooey-gooey cheesy goodness.
Caramelized onions can be made ahead of time and stored in an airtight container in the fridge for a week or more. You can also freeze them for up to two months.
The soup itself can be made up to 3 days ahead (without toast and cheese) if refrigerated, or up to 6 months ahead if frozen. The toasts can be made (without cheese) and kept sealed at room temperature for up to 3 days. Dinner can be as simple as warming the soup and adding the topping!
Your reward for a long, lazy afternoon's work will be a delicious, cozy dinner. Along with a glass of wine, you'll have something wonderful to share on a cold day with someone you love.
Slainté! L’chaim! Cheers!
Tammy
Related Recipes
Here are just some ideas of recipes you can make for dinner.
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Recipe
Homemade French Onion Soup with Beef Stock
Equipment
- kitchen twine
Ingredients
For the soup
- 5 tablespoons unsalted butter, divided, see Recipe Notes
- 3 pounds onions, yellow or sweet (Vidalia or Walla Walla, preferred), about 4 to 6 medium
- 2 teaspoons kosher salt
- ½ teaspoon black pepper
- 1½ cups dry white wine, see Recipe Notes
- 10 sprigs fresh thyme
- 2 bay leaves
- 4 cups beef stock, or store-bought low-sodium beef broth
- 2 cups water
- ½ to 1 teaspoon granulated sugar, optional
For the topping
- 1 baguette, sliced
- 1 garlic clove, cut in half lengthwise
- 2 teaspoons sherry, cognac, or cointreau (optional)
- 1 cup Gruyère, or Emmentaler cheese, grated
Instructions
- Caramelize the onions: Cut the onions in half from the top to the root. Thinly slice the onions using a mandolin slicer, sliding the onion across the blade sideways (the narrow part facing forward). Be sure to use the finger guard to protect your fingers. If you don't have a mandolin, slice the onions thinly with a chef's knife.
- Melt 3 tablespoons of butter over medium heat in an 6-quart enameled cast-iron pot (or another large heavy pot with a lid). Add the onions, sprinkle them with 2 teaspoons of salt, then cover and cook until the onions have heated through and started to steam, about 10 minutes.
- Uncover the pot, stir in the black pepper, then reduce the heat to low and cook, stirring occasionally, until the onions have caramelized, about 3 hours.
- Make the soup: When the onions have completely cooked down, (the liquid has evaporated, and the onions have turned amber), add the wine and raise heat to high. Cook until almost all liquid has evaporated, about 15 minutes.
- Tie the thyme and bay leaves into a bundle (aka bouquet garni) with kitchen twine. Add the stock, water, and the bouquet garni to the pot with the onions. Bring to a boil (this can take about 15 minutes). Reduce to a simmer and cook, uncovered, until the soup has thickened, 20 to 30 minutes.
- Remove the pot from heat, remove the bouquet garni, and whisk in the remaining 2 tablespoons of butter. Taste and adjust the seasoning as needed. If desired, you can add ½ to 1 teaspoon of sugar if the soup isn’t sweet enough for you.
- Prepare the bread slices: Cut two ½-inch slices of the baguette for every serving of soup (make sure they will fit in the ramekins). Lightly toast the slices in the toaster until they are crisp and dry but not browned. Alternatively, preheat the oven broiler and place the bread slices on a half sheet baking pan. Broil until the slices, about 1 minute per side.
- Rub one side of each toast with the garlic clove and set aside.
- Assemble the soup: Add ½ teaspoon of sherry (if using) to the bottom of four 16-ounce oven-safe ramekins, then ladle the soup on top. Top each serving of soup with the two garlic-rubbed toasts. Divide the cheese among the servings, covering the bread and some of the soup.
- Carefully broil the tops of the soup with a chef's torch until cheese is melted and bubbling, or place the ramekins on the half sheet baking pan and transfer to oven to broil and melt the cheese, about 4 to 8 minutes. See the Recipe Notes for finishing the soup in non-oven-safe soup bowls.
- Serve and enjoy your afternoon's labors!
- Caramelized onions can be made ahead of time and stored in an airtight container in the fridge for a week or more. You can also freeze them for up to two months.
- The soup itself can be made up to 3 days ahead (without toast and cheese) if refrigerated, or up to 6 months ahead if frozen. The toasts can be made (without cheese) and kept sealed at room temperature for up to 3 days.
