SLOW COOKER FRENCH ONION SOUP

Slow Cooker French Onion Soup is a comforting, classic dish that brings warmth and flavor to any table. With the right ingredients and a little patience, this easy French onion soup becomes a rich and satisfying meal that highlights the sweet, caramelized onions beautifully. 

This crock pot French onion soup recipe is perfect for a cozy dinner, offering a blend of savory beef stock, aromatic herbs, and a delightful layer of melted cheese over crusty bread. The slow cooker simplifies the process, allowing the flavors to meld together as it does the work while the cook attends to other tasks.

What is traditional French Onion Soup?

There are many versions of this wonderful soup recipe across European cuisines, however, the classic French Soup is the most famous one. Classic French Onion Soup is made with beef broth and includes some type of alcohol like Cognac or Brandy. Other versions might include chicken stock instead of beef stock and white wine, and some do not include any alcohol.  

The defining feature is the soup is topped with a slice of baguette. This is placed on the soup just before serving and often covered with melted cheese. Choices for cheese include Swiss, Gruyere, or Parmesan, which create a delicious, gooey layer!

How do I get perfect Caramelized Onions?

The key step for this delicious soup is the proper caramelization of the onions. I am talking about the long and steady process where onions become translucent and golden brown with the caramelization of their natural sugars.

Caramelization starts with cutting all the onions in same-sized pieces, so they cook evenly. The best is to slice them thinly so they can cook a bit quicker. Then follows the melting of a couple of tablespoons of butter and cooking the onions on slow heat with a bit of salt so they release their juices. Keep stirring every now and then and let them do their thing on very low heat (that is key!) so they do not burn.

The key step is to make the onions “sweat” slowly, stirring occasionally until they achieve its golden translucent perfection, and for this, it requires time. Depending on your pan size and the number of onions you have used, it might take something from 45 mins to 1 hour. I am sorry there is no shortcut for this step, but it will be worth if for the final results! 

Ingredients for Slow Cooker French Onion Soup

Onions: Use 5-6 large yellow onions or sweet white Vidalia onions.

Butter: You need 4 TBSP of butter to help caramelize the onions.

Brandy or cognac: Using ½ cup brandy or cognac to add richness to the caramelized onions, as said do not worry about the alcohol content since it will be evaporated while cooking.

Beef stock: Add 6 cups of beef stock, store bought or homemade.

Flour: Using 3 TBSP of white flour will help thicken the soup.

Herbs: You will need 2 bay leaves, 4 sprigs of fresh Thyme or 1 teaspoon dried, plus a little more for the final garnish. Try to avoid using Rosemary since it is an overpowering taste and may alter the recipe results.  

Salt & Pepper: Add salt and pepper to taste, add a small amount of each at a time and consider doing this step when you are ready to eat.  

Bread: Use 1-2 slices of baguette bread per bowl.

Grated Cheese: The popular choices of cheese are Swiss, Gruyere, Gouda, Parmesan, or Mozzarella. You can use almost any cheese that melts well, Parmesan makes for a great topping to the soup.  

Worcestershire Sauce: This is an optional ingredient, feel free to add it to your soup, but I personally don’t find it necessary. 

How to make Slow Cooker French Onion Soup

Prep

Start by slicing the onions thinly, the thinner the better so they cook a bit faster.

In a large pan on medium heat, add the butter and melt it. Add the sliced onions and let them cook for 1 minute or so before you stir them. Then add a little bit of salt to the onions and mix well, turn to low heat and keep stirring every 5 minutes or so. 

When you start to see the onions browning, add a splash of cognac to deglaze and keep cooking until all the onions are translucent and a soft golden brown. 

Add in the flour and cook it for 1-2 minutes or so, stirring constantly to avoid it from burning. Now add a splash of the beef stock and dilute the flour in it and mix well to combine.

Once the flour has mixed well and completely dissolved, transfer the caramelized onions from the pan to the slow cooker. Continue to add the rest of the beef stock and herbs to the slow cooker and mix well. 

Cook

Set the crockpot on low heat and cook for 5-6 hours. Towards the last 30 minutes, carefully taste the soup and add the salt and pepper as desired.

Assemble bowls

Preheat the oven to 400º F. Slice the baguette bread, place it on a baking sheet and toast bread for 5-7 minutes.

In oven safe soup bowls pour the onion and broth mixture into each bowl, top each bowl with 2 slices of bread and add grated cheese on top.

Change oven setting to broil, place the full soup bowls in the oven and broil for 8-10 minutes. Be very careful when removing them from the oven!

Serve and enjoy!

Instructions for Stovetop method

Prep

Follow the same instructions as in the Slow Cooker Method, except use a Dutch oven or large pot.

Cook

Set the heat to low and let the mixture cook for 5-6 hours.

Towards the last 30 minutes, carefully taste the soup and add the salt and pepper as desired.

Assemble bowls

Complete the same steps as in the slow cooker method to assemble and complete each soup bowl.

Enjoy!

What type of onions should you use for French Onion Soup?

Although is possible to make it with any type of onion (believe me I’ve tried it!) my personal recommendation is to make it with yellow onions or sweet white onions like Vidalia onions. They give the soup a fantastic flavor and the texture is just right using these types of onions.

How do I make this recipe if I do not have oven safe bowls?

If you find yourself craving this savory soup but you do not have oven-safe bowls, we’ve got you covered! Prepare everything the same except you add the cheese to the bread BEFORE you broil it. This way your cheese is melted and your bread is toasted, then add the cheesy bread to the bowl of onion and broth soup.

Can I make this a vegetarian or vegan soup?

You can make this soup vegetarian or vegan by substituting the butter with olive oil and using vegetable broth instead of beef broth. Add vegan cheese or skip it entirely, however, that would result in a bit of a sad soup. There are so many great alternative options these days, you do not have to miss out due to dietary restrictions anymore!

How long will this French Onion Soup last?

It can be stored in the fridge for up to 6 days in an air-tight container, obviously, without the toasted bread + cheese on top. When you are ready to enjoy, toast your bread and melt your cheese!

For more great soups & stews, try our favorite recipes here:

• Copycat Panera 10 Vegetable Soup
• Butternut Squash Soup
• French Onion Tomato Soup
• Easy Vegetable Chowder
• Tomato Basil Soup
• Classic Chicken Noodle Soup
• German sausage soup
• Crockpot ham and bean soup
• Lemon Chicken Vegetable Soup
• Zucchini Sausage Soup
• Lasagna Soup
• 20 Minute Loaded Baked Potato Soup
• Slow Cooker Creamy Chicken Enchilada Soup

Slow Cooker French Onion Soup is a delicious dish made with rich beef broth, savory, sweet onions and topped with crusty bread & cheese! This easy French onion soup is a comforting and filling meal the whole family will love.