A friend recently asked me about French onion soup and I realized how long it’s been since I made it. I love homemade French onion soup but what I don’t love is standing at the stove for an hour or more caramelizing a huge batch of onions. So, on a recent weekend when I had a lot of projects to do at home, I decided I’d toss the onions in my crockpot and let it do most of the work.

Crockpot French Onion Soup Recipe

• 4 tablespoons butter
• 2.5 lbs. sweet onions, cut in half from root to top and then sliced thin
• 1 teaspoon olive oil
• 1 teaspoon kosher salt
• 1 heaping teaspoon flour
• 51/2 cups homemade or good quality beef broth (for vegetarian French onion soup, substitute vegetable broth)
• 1/2 cup dry red wine
• 1 teaspoon dried thyme
• 1 bay leaf
• Freshly ground black pepper

For serving:

• French bread, cut into slices
• Grated gruyere or cheese of your choice

Total cooking time is approximately 8 – 8 1/2 hours.

Edit: As a side note, I had a reader tell me that after cooking the onions for 5.5 hours as directed below, there was still so much moisture in the crock that the onions weren’t caramelizing. If this is the case, try tilting the lid for an hour or so, to let the moisture escape and help the onions caramelize.

Directions:

1. Rub the inside of the crock with butter and reserve the rest
2. Add onions to the crockpot
3. Drizzle onions with olive oil
4. Sprinkle salt over onions and toss well
5. Pat the onions down into the crock – don’t smash them, just gently press them down so they’re somewhat compacted
6. Place remaining butter on top of onions
7. Cover the crockpot and turn on high

Cook the onions for 5 – 5 1/2 hours, stirring every hour or so. At the end of this time, your onions should be beautifully caramelized.

Now, on to finishing your soup:

1. Sprinkle the flour over the caramelized onions and stir well
2. Cover and cook for a half hour
3. Add beef broth, wine, thyme, bay leaf and pepper
4. Stir well, cover, and cook 2.5 hours longer on high

Turn off heat, remove bay leaf and discard, ladle soup into bowls and serve with crusty bread topped with melted cheese. For the cheesy bread, I simply slice my French bread, place the slices on a sheet pan lined with aluminum foil and broil for a few minutes until one side is nicely toasted. Then, turn the bread over, top the untoasted side with cheese and place back under the broiler for a few more minutes, until the cheese is bubbling and starting to brown.

I like to serve my toasted cheese bread on the side but if you prefer, you can place oven-safe bowls filled with soup on a sheet pan, top with bread and cheese, and then broil until the cheese is bubbling and starting to brown.

This soup is dark, rich and flavorful. I’m a big believer that homemade beef stock makes a world of difference here so if you don’t have homemade broth, be sure to buy the best you can.

If you want to make a vegetarian French onion soup, simply replace the beef broth with homemade or good-quality vegetable stock. The finished soup will be a little lighter in flavor but it’s just as delicious, trust me. I was vegetarian for a couple of years and made this a number of times during that period.

While making this crockpot French onion soup is easy, it’s not a throw-it-in-and-forget-it dish. It still takes a little watching and maintenance to be careful that the onions don’t burn. Every crockpot is different, so keep an eye on your onions in the first hour or two.

The all-day aroma of caramelized onions cooking makes this totally worth making and letting my crockpot do a lot of the work freed me up to do other things. That’s a win-win in my book.

Enjoy!