Name: French Onion Soup with Slow Cooker Instructions
Prep time: 1 h
Cook time: 13 h
Total time: 14 h
Yield: 6
Cuisine: French
Ingredients: 4 pounds yellow onions; 4 tablespoons butter, divided; 4 tablespoons vegetable, canola, or extra virgin olive oil, divided; Salt and ground black pepper; 1 tablespoon all-purpose flour; 2 teaspoons dried thyme leaves (or 1 teaspoon ground dried thyme); 1 cup dry white wine; 4 cups (1 quart) beef broth or stock, or Better Than Bouillon Beef Base mixed with water; One French baguette; 8 ounces gruyere cheese, grated; About 1/4 cup chopped fresh chives

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French onion soup is a delicious reminder that the best things in life are often the simplest.

Cooking onions low and slow for hours transforms them into something rich, slightly sweet, multi-layered, and utterly satisfying. After that, all that's needed is a flavorful broth, a baguette, and plenty of bubbly, melted cheese for a meal that's both humble and elegant, equally perfect for cozy evenings at home and fancy dinner parties. This recipe makes homemade French onion soup easier than ever with instructions for cooking the onions in your slow cooker.

A bowl of french onion soup sprinkled with chives and ready to eat.

Traditionally, French onion soup is made by cooking onions for a long time on the stove top over low heat until they are rich golden brown. This makes a delicious, flavorful broth, but it's also time consuming and requires you to be attentive for the several hours that the onions are cooking.

Cooking the onions in a slow cooker is much easier and makes a rich and flavorful soup with minimal hands-on effort. In fact, I often set my slow cooker to cook the onions overnight, while we sleep.

The challenge with most slow cooker french onion soup recipes is that the end result doesn't have the same amount of richness and complex flavor as when the soup is cooked for a few hours on the stovetop.

To solve this problem, this recipe calls for cooking the onions in the slow cooker until they are deeply caramelized and then finishing the soup on the stovetop. The combination of slow cooker and stovetop cooking gives you the best of both worlds - rich, complex flavor and very little hands-on time.

This process also allows you to cook the onions up to 3 days in advance if you like.

This recipe is unfussy, easy to adapt to your schedule, and still delivers cozy, deliciously flavorful, cheese covered bowls of French onion soup. What could be better than that?

-Rebecca

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Ingredients needed to prepare this recipe
Substitutions:
Step-by-step photos and instructions
French onion soup bowls
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Ingredients needed to prepare this recipe

All the ingredients needed to make slow cooker french onion soup.

Yellow onions: I prefer using yellow onions to make French onion soup because they have a mild, natural sweetness and even flavor.
Butter and oil: Butter for flavor and oil to keep the butter from burning.
Salt and ground black pepper
All-purpose flour: Just one tablespoon is all you need to give the broth some body.
Dried thyme
Dry white wine: My favorites are Sauvignon blanc, Pino Grigio or Pinot gris, or unoaked Chardonay
Beef or Vegetable Stock (or Better Than Bouillon Base mixed with water)
French bread
Gruyere cheese (see below for substitutions)
Fresh chives

Pro tip! Use a food processor to chop your onions! Making French onion soup requires a LOT of eye-watering onion chopping which is why I like to use my food processor. Peel and cut the onions into quarters and then slice them using the slicing blade of your food processor. Your eyes will still water, but the process will go much faster.

Substitutions:

Instead of Gruyere: French onion soup is traditionally made with Gruyere cheese but these varieties are a good alternative if you don't like, or can't find, Gruyere: Swiss, Asiago, Mozzarella, and Pecorino Romano
To make gluten-free french onion soup: Omit the flour and instead make a cornstarch slurry. Reserve ½ cup of the beef broth and slowly stir it into 1 tablespoon of cornstarch. Stir this mixture into the saucepan after adding the wine and the rest of the broth. Use your favorite gluten free bread in place of a French baguette.
To make vegetarian French onion soup: swap the beef broth for vegetable broth or Better Than Bouillon Vegetable Base mixed with water.

Two bowls of french onion soup topped with chopped fresh chives and ready to eat.

Step-by-step photos and instructions

Sliced onions on top of a cutting board.

Remove the outer papery layers of the onions, cut them in half, and then cut into ¼-inch slices. I usually do this in the food processor. After cutting the onions in half, feed them through slicing disk in your food processor.

Caramelized onions in the bowl of a slow cooker.

Pile the sliced onions into the bowl of your slow cooker, add some butter and oil, season with salt and pepper, and cook on low for about 12 hours, until the onions are dark golden brown.

Make-ahead tip! Once the onions are caramelized, they can be stored in the refrigerator in an airtight container for up to 3 days.

Caramelized onions cooking on the stovetop in an enameled cast iron pan.

Transfer the caramelized onions to a large saucepan, stockpot, dutch oven, or braiser that's at least 3.8 quarts in size. Set the pan over medium heat and cook, stirring occasionally, until the onions are piping hot.

Using a wooden spoon to stir flour and thyme into caramelized onions while they cook in a pan on the stovetop.

Sprinkle in some flour, dried thyme, and ground black pepper. Cook, stirring, for 1-2 minutes.

Caramelized onions cooking in white wine and beef stock.

Slowly pour in some dry white wine and beef stock. Bring the liquid to a boil, then partially cover the pan with a lid and let everything simmer for about an hour.

Caramelized onions that have been cooked in broth for about an hour.

Taste the broth, add more salt and pepper if you like, then ladle it into oven proof bowls.

Set the bowls on a parchment lined rimmed baking sheet and turn on your oven's broiler or preheat the oven to 475° F (246° C).

Baguette slices cooking in a skillet until toasted and golden brown on both sides.

Cut the baguette into 2-inch slices and toast in a large skillet with some butter and oil, until golden brown on both sides.

Two bowls of onion soup that have been topped with a couple of toasted baguette slices and some grated gruyere cheese.

Top each bowl with a couple of toasted baguette slices and a generous handful of grated gruyere cheese.

Two bowls of french onion soup with blistered, melted cheese that have just been removed from the oven.

Bake or broil until the cheese has melted, is bubbling, and browning in spots.

Sprinkle the hot bowls of French onion soup with a handful of chopped fresh chives and serve.

Someone using a spoon to lift a bite of french onion soup from a bowl.

French onion soup bowls

Before my husband and I moved into an RV to travel full-time, I had a set of these Lion's Head French Onion Soup Bowls that I used exclusively for French onion soup.

I just loved them and if it wasn't for the limited space of my new tiny kitchen, I would have kept them forever. If you have the space, and the inclination, serving French onion soup in these delightful bowls makes the whole experience feel more elegant and authentic. You can almost pretend you're in a little French cafe somewhere in Paris. Almost.

A spoonful of crock pot French onion soup.

If you give this recipe a try, let me know! Scroll down to leave a comment and rate it!

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Yield: 6 servings

French Onion Soup with Slow Cooker Instructions

French onion soup is a delicious reminder that the best things in life are often the simplest. This recipe makes homemade French onion soup easier than ever with instructions for cooking the onions in your slow cooker.

Prep Time 1 hour

Cook Time 13 hours

Total Time 14 hours

Ingredients

4 pounds yellow onions
4 tablespoons butter, divided
4 tablespoons vegetable, canola, or extra virgin olive oil, divided
Salt and ground black pepper
1 tablespoon all-purpose flour
2 teaspoons dried thyme leaves (or 1 teaspoon ground dried thyme)
1 cup dry white wine
4 cups (1 quart) beef broth or stock, or Better Than Bouillon Beef Base mixed with water
One French baguette
8 ounces gruyere cheese, grated
About ¼ cup chopped fresh chives

Instructions

Remove the outer papery layers of the onions, cut them in half, and then cut into ¼-inch slices. I usually do this in the food processor: After cutting the onions in half, feed them through slicing disk in your food processor.
Pile the sliced onions into a slow cooker. Cut two tablespoons of butter into small pieces and dot the pieces over the top of the onions. Drizzle 2 tablespoons of oil over the top of the onions and sprinkle with a bit of salt and ground black pepper. Top the pot with the lid and cook on low for 12 hours, until the onions are very soft and a dark golden brown. (I usually set them to cook overnight.)
Transfer the caramelized onions to a large saucepan, stockpot, dutch oven, or braiser that's at least 3.8 quarts in size. Set the pan over medium heat and cook, stirring occasionally, until the onions are piping hot.
Sprinkle the flour, thyme, and some additional ground black pepper over the onions and cook, stirring constantly, for 1-2 minutes.
Slowly pour in the wine and beef stock. Bring the liquid to a boil, then partially cover the pan with a lid and let everything simmer for about an hour. (Leave the lid on the pan askew so that steam can escape.)
Taste the broth, add more salt and pepper if you like, then ladle it into oven proof bowls. Set the bowls on a parchment lined rimmed baking sheet and turn on your oven's broiler or preheat the oven to 475° F (246° C).
Cut the baguette into 2-inch slices. Plan on 2-3 slices per bowl of soup, depending on how thick your baguette is.
Add the remaining 2 tablespoons of butter and oil to a large, 12-inch skillet and set it over medium heat. When the butter has melted, add the baguette slices. Toast the bread, turning from time to time, until all the slices are golden brown on both sides.
Top each bowl of soup with a couple of toasted baguette slices and a generous handful of grated gruyere cheese.
Place the tray in the oven and bake or broil until the cheese has melted, is bubbling, and is browning in spots.
Remove from the oven, sprinkle each with a few chopped chives, and serve.

Notes

Make-ahead tip! Once the onions are caramelized, they can be stored in the refrigerator in an airtight container for up to 3 days.

Alternatives to Gruyere cheese: Swiss, Asiago, Mozzarella, or Pecorino Romano

To make gluten-free french onion soup: Omit the flour and instead make a cornstarch slurry. Reserve ½ cup of the beef broth and slowly stir it into 1 tablespoon of cornstarch. Stir this mixture into the saucepan after adding the wine and the rest of the broth. Use your favorite gluten free bread in place of a French baguette.