Oh so simple and oh so good. Better than restaurant quality, this Crock Pot French Onion Soup is an elegant classic soup for everyday or special meals.
Editors’ Note: Originally published July 12, 2015. This recipe has been updated with expanded test and information and the photos re-edited.
I love a good French onion soup. I mean really love it. If it’s on the menu, I usually make sure I have it.
Unfortunately, that means the good, the bad and the ugly. I should put adequate on that list too. I can live with adequate, but most seem to be wanting and falling into the bad/ugly range.
A good onion soup is more than a beef broth with some caramelized onions. You need to get the caramelization going, or you have nothing. You need some long cooking.
While many techniques require multiple rounds of caramelization on the stove top, you can do it in a crock pot. I’m lazy… I pick number two.
Start by loading a slow cooker with some chopped up onions. Cook with butter, salt, pepper, and thyme. Add a little Worcestershire sauce to deepen the flavor. Cook on high for a long time add the broth and cook a little longer. The serve your favorite way. Yum…
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Very nice solid lower 5. You can make a little better French onion soup but with a lot more work. Much better than most restaurants. I have had only a few better.
Pro Tips: Notes on Crock Pot French Onion Soup
This recipe can be easily double but could also be cut in half. Some crusty bread is used to float cheese on top. You can use what you want, but a nice crusty French baguette is my choice. For the cheese we like provolone, but some prefer gruyere or some Swiss.
What ingredients to use?
With many recipes, you can use cheaper generic ingredients. With so few ingredients, quality matters here. So only use ingredients you trust which could be cheaper generic if you know them well.
Very few commercial beef broths are above adequate, and many are just bad. I used Swanson broth here. I think it has improved in quality over the years and is quite good now. The Swanson stock is also good, but I detect no difference in use, so I don’t spend the extra money.
I’m using Lee and Perrins Worcestershire Sauce which I trust, but I suspect there are other good choices. Worcestershire sauce will make the “beef” flavor really pop. It can be used in many cooking applications to boost that beef test, especially when using beef broth.
What onions for onion soup?
Sweet onions like Vidalias, Mauis, Walla Wallas are probably not the best idea here. I don’t like much sweetness here. So regular yellow or white onions are good. I consider white and red onions equivalent to my usual yellow onions and some people like a mix.
Comments on Crock pot Temperature:
One reader, Dan in the comments, had trouble with 9 hours on high burning. While high on a crock pot should be in the 250-300 degree range, some will run over 300 degrees, and that is probably the issue Dan and a few others have had.
So be advised that some crock pots may run hotter so watch for ‘softened and deep golden brown” as the endpoint for the onions being done. I would say if your crock pot ever boils on low, it may be in the “runs hot” category, then use low for this recipe.
My 9-10 hours on high stands and is consistent with other similar recipes and less than Cooks Illustrated which is 10-12 hours on high.
Start with simple ingredients.
Chop 1 1/2 pounds of onions about 3 medium size onions. Some people will want rings or some petals. Add to a smaller crock pot. If doubling recipe then a full-size crock pot is correct.
Add one teaspoon coarse salt, two tablespoons butter, 1/2 teaspoon pepper, 1 1/2 teaspoon Worcestershire sauce and 1/2 teaspoon thyme. The butter can go in unmelted, but you will need to stir in 1 hour or melt it first in the microwave.
Cook on high for 9-10 hours until nicely darker brown. Be warned that some crock pots may run hot and please watch for the endpoint and don’t go by time alone. Then add 4 cups of beef broth and cook on high for at least one hour more.
Preheat broiler to high. Arrange ramekin or oven-safe bowls on a cookie sheet. Ladle hot soup it into the bowls, float toasted crusty bread on the soup.
Covered each bowl with cheese of your choice.
Broil until cheese is bubbly and golden, 2-4 minutes.
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Originally published July 12, 2015.