Name: Crockpot French Onion Soup
Prep time: 20 min
Cook time: 275 min
Total time: 295 min
Ingredients: 4 large yellow onions (thinly sliced); 4 tbsp butter; 1 tbsp brown sugar; 1 tbsp minced garlic; 32 oz beef broth (1 carton); 1 tbsp Worcestershire sauce; 1/2 tsp salt (plus more to taste); 1/2 tsp black pepper; 8 baguette slices (about 1/2 inch thick); 5 oz Gruyère cheese (shredded, about 1 1/2 cups)

Deep browned, sweet onions simmered in savory, rich beef broth and topped with a slice of crusty baguette and bubbling, browned Gruyère cheese, this Crockpot French onion soup tastes just like your favorite bistro’s version! If there’s one soup that people seem to love ordering at bistros, it’s probably French onion soup. Luckily, this French onion soup recipe can be easily made at home in the slow cooker! Instead of standing over a pot all afternoon, simply toss everything into your Crockpot and let it simmer away. It’s easy to make a bowl of bubbling, savory soup at home with this recipe!

French onion soup is one of those dishes that practically sells itself! Once it comes out of the oven and hits the table the aroma of melted cheese wafting from the broiler will have everyone coming over to take a peek! After many years in restaurant kitchens I can attest to this! The only difference with this recipe is that we’re letting the crock pot do all of the long slow simmering for us so we can get on with our day!

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What You Need

You’re going to need 4 big yellow onions, half a stick of butter, a spoonful of brown sugar, a tablespoon of minced garlic, a 32 ounce carton of beef broth, Worcestershire sauce, salt and pepper, a baguette and a block of Gruyère. That’s it!

Yellow onions, beef broth, Worcestershire, Gruyère, butter, brown sugar, minced garlic and a baguette

I used Pacific beef broth and a 4.9 ounce block of Swiss Gruyère (don’t substitute mozz if you can help it). If you can’t find Gruyère use Swiss or even a Swiss/provolone combo. The Gruyère adds a nice salty/nutty flavor, melts nicely and browns nicely under the broiler (tastes more like the restaurant version). Jarred garlic is totally acceptable in a soup like this.

Caramelize the Onions on the Stove First

Slice onions into thin half moons (peel, then slice in half, top to bottom, before slicing into half moons). Don’t be intimidated by the amount of onion, as they’ll cook down quite a bit!

Thinly sliced yellow onions piled on a cutting board

You’ll need your largest skillet for this, as you’re going to brown a lot of onions in it. This step can’t be skipped or French Onion Soup won’t taste like French Onion Soup. I’ve seen recipes that tell you to put raw onions into the crockpot with the broth and, let’s be honest, that’s just onion soup with extra steps. Melt butter in your large skillet over medium heat, add onions and brown sugar (the brown sugar will help give the onions a jump-start towards that sweet, dark color we’re after), and cook until onions are deeply browned, stirring occasionally.

Sliced onions with butter and brown sugar in a large skillet

Continue to stir the onions every few minutes. For the first 10 minutes or so, all that will happen is that they’ll release a lot of liquid and get soft. Don’t despair! Soon that liquid will cook down and the onions will begin to brown. Bits will start sticking to the bottom of the pan, which you should scrape up as you stir since those browned bits taste good.

Cook, stirring occasionally, until deep, rich brown, the color of an old penny, about 25 minutes for mine. Reduce heat and add a splash of broth if at any point the mixture begins to scorch. Add garlic during the last minute of cooking so it doesn’t burn.

Deep brown caramelized onions in a skillet

Let the Crockpot Do the Rest

Scrape the onions into the slow cooker. Pour a splash of the broth into the hot skillet and swirl it around to get all the good stuff stuck to the bottom, then pour that in too, along with the rest of the broth, the Worcestershire, and salt and pepper.

French onion soup cooking in a Crock-Pot

Cover and cook 4 hours on high or 7 to 8 hours on low. After it’s cooked that long, the onions and beef broth will meld together beautifully. Season with salt to taste, because I find it’s best to season broths at the end since they vary so greatly in saltiness.

The Bread and Cheese Topping

When the soup is cooked, preheat the broiler. Place oven safe soup bowls or ramekins on a baking sheet (yes, the cheese WILL dribble down the sides, trust me!) and fill almost to the top with soup. Place two slices of the baguette on top of each bowl so they float.

Ramekins of French onion soup topped with baguette slices

Shred the Gruyère and add it to the bowl. Make sure to sprinkle it to the edges of the bowl so everyone gets some of that crispy browned cheese goodness!

Shredded Gruyère piled on ramekins of soup on a baking sheet

Broil Until Bubbly

Place pan in the broiler and leave until the cheese is melted and slightly browned in spots, about 5 to 7 minutes. Do not walk away as broilers can take dishes from cooked to burnt quickly.

French onion soup bubbling under the broiler

Let them sit for about 5 minutes after they come out of the oven as they are extremely hot and the soup in the bowl holds a lot of heat too. I like to break through the top with a spoon and eat a bite of bread, cheese and onions in each spoonful.

Four ramekins of French onion soup with browned Gruyère on a wood board

Making It Ahead and Leftovers

This soup will keep for 4 to 5 days in the fridge or up to 3 months in the freezer. Leftover soup tastes even better the next day. I filled four ramekins and still had a ton of soup left in the crockpot (never a bad thing). Refrigerate or freeze the soup only (not with the bread and cheese). To serve, reheat soup on the stove top and pour into a ramekin. Add a piece of baguette and sprinkle with Gruyère and broil until bubbly and golden brown. Enjoy!