Slow Cooker French Onion Soup

I thought this was delicious and authentic tasting with the fresh thyme sprigs andgruyere topping. Just be warned your house will have a strong onion-y fragrance, so keep the kitchen fan going!

Amazing given the cooking method. I have always used the French approach starting with roasting beef bones. Of course it will always be better. But given the convenience of a slow cooker, the results were stunning. The key is in fully carmelizing the onions and reducing liquid to a minimum. The brand of cooker will alter cooking time. Mine took 13 hours, so I have noted in my recipe to start a day ahead.
The soup was a bit oily, so reduced butter by half. I was fine with the 1 T sugar, but 2 would be enough. I used 8 cups of low salt beef broth, 1 T cognac, 1/2 tsp ground pepper, salt to taste just before serving. My family likes a lot of cheese so increased the quantity of the Gruyere per bowl.
My family was wowed!

This was great! I tweaked it to make it vegetarian so used half mushroom stock half red wine instead of beef stock. Also added a tablespoon of low sodium Worcestershire sauce to give it more depth. I halved the recipe and it was more than enough for two plus leftovers. In the end I did end up needing more salt but added it before serving. Delicious!

My review from Feb. 2021: Made this yesterday. I did not find that cooking the onions on HIGH resulted in them burning or turning to mush, indeed by 8 hours they were just starting to brown, so I added another hour. I also cooked for 45 minutes instead of 30 after adding the broth. 2 Tb. of grated cheese is about 1/2 the amount you need to use as well. Next time I plan to cut the recipe in half, as this is a lot of soup for a solo diner! I'll see how it does with freezing.

Addendum: I have made this several times now, and find the 9 hours on high, and 45 min after adding the broth is about right. It also freezes well in portion sized containers and is easy to microwave to reheat and then add the bread and cheese and broil.

I’m surprised at the bad reviews. I made exactly as stated the first time and it was too sweet for me. I made again with just yellow onions - not sweet onions and no sugar. Loved it! I think I’ve made it 6 or more times since then since it works in the freezer and I send extras to in-laws or my mom. I’m making it again today with yellow and two white onions. I do cook the full 8 hours and sometimes longer. If this is the first time cooking it, I highly recommend checking it every few hours. I have found some slow cookerls highs are too hot for this recipe. I use my older slow cooker for this recipe since it is a more even temp.

I was so proud of myself. I had my onions all freshly cut and the crockpot going by 9:15 am. 4 hrs later, I was disappointed to find a blackened, burnt mess :-(

I followed this recipe to the tee and it was fantastic I wouldn't change a thing!!!

Well did what recipe asked and onions mostly burnt so ya, bad recipe atleast for the onion section, dont cook on “high” for 8hours unless you want burnt onions and ruined soup

I read the comments before I started and discovered that it takes the FULL 9 HOURS for the onions to properly caramelize, not 5 like some posters have stated. If you don't let them cook for the full time, your soup is not going to taste as good. The finished product was delicious! The only deviation I made was to add a half cup of dry sherry at the finish. I will be making this again, so great to not have to stand at the stove for an hour caramelizing onions!

I had no idea one could caramelize onions in a slow cooker!  Once a year, my hubby will make up a batch of Julia Child's French Onion Soup and it is simply to die for.  This isn't that good, but we still were impressed with the outcome.  I omitted the sugar, but wish I hadn't now.  It did not seem overly sweet to us.  I also did 1 tablespoon of red wine vinegar and 1 tablespoon of pinot noir.  While it was fine, I can't help but wonder if using cognac - as Julia Child does - would add to the richness of the finished soup.  Will try that next time.  A combo of the gruyere along with some sharp cheddar and parmesan (to equal the 7 oz) was a perfect topping.  I also only cooked the onions for 5 hours.  Having a food processor really helps decrease the slicing time and the tears....

Did not care for this recipe.  Very sweet for both my husband and me - even without added sugar.  I only used 1/3 sweet onions and the rest were mixture of red onions and yellow onions.   8 hours was too long in a slow cooker.and the onions were almost pure mush.  We each had one bowl and threw the rest out.  I will keep looking for another recipe.  Other sites suggested dry white wine and cooking on the stovetop to keep a better watch on the onions.  One site said one hour was just about the right amount time to cook the onions down and get out all the flavor.  I was surprised that this recipe had such good reviews. 

I wish I had read the reviews here before I made this.  It was indeed way too sweet.  I'm glad I tasted it before serving it.  I decided to add about a cup of red wine and the hard edge of the gruyere into the pan and simmered it (in a dutch oven on the stove) a while longer.  I then tasted it again and thought it was still off so I added the rest of the second container of broth/stock that I had on hand and simmered it some more.  It was good enough to eat at this point (3-stars), but I will not be making this version again (as written 2-stars).

We thought this soup was amazing.  I followed the recipe exactly and my husband and I did not think it was too sweet or that the red wine vinegar tasted odd.  I used the mandolin for slicing the onions which made it pretty quick and easy.  Will definitely be making again and would be super easy to serve to guests.

I made this for my older teenagers and everyone really like it.  I followed an earlier comment and added a little red wine and didn't add the vinegar.  Otherwise, I followed the recipe.  Also, we didn't think it was too sweet, as some earlier comments mentioned.  I'm sure that's just personal taste.  We'll definitely make again!  

This was my first effort at French onion soup. I made it as directed. Agree with another reviewer about cutting or omitting the vinegar, and another who added some red wine. There was also almost too much onion, so I will scale that back to four medium to large vs five. After cutting the onions, the rest was a breeze, so I am upping the star rating.

This was my first attempt at making French onion soup. It was really good! I used less onion, 4 large yellow onions, and less sugar, only half tablespoon, as some reviews suggested. I also used cooking sherry instead of the red vinegar. All in all, it was very easy and very tasty! I did have to move it outside to cook as it filled my entire house with the very aromatic onion smell! Not a fan with the kids! But good to eat!! Thumbs up!

I like the cooking method but next time I would leave out the vinegar. Should have trusted my original instincts on that one. Other than that it was pretty good.

Perhaps my Vidalia's were too sweet--they are just starting to show up in the grocery, and the soup was too sweet. And perhaps the onions are too juicy too since they didn't really caramelize, rather they just cooked down. I might try again with yellow onions and just a pinch of sugar (if it's really even necessary for the caramelizing process). Not sure if I'll try it again.

The chopping of onions was not fun but the result was worth it.  The Gruyere cheese and bread on top really made it tasty!  We had a few friends for dinner and everyone seemed to really enjoy it.  I will try the suggestion of adding some red wine to it next time, too.  

Made this for our "Taste of Spring" themed supper club and it was very well received.  I loved the sweet onion flavor.  I served smaller portions in mugs to go with the rest of the tasting menu.  Reheated it was even better the next day.  I used my food processor to slice the onions, so between that and the slow cooker it was like this dish made itself. I did find that 5 hours on high was long enough to caramelize the onions.

This was fabulous!!!  Loved the sweetness of the onions.....all the slow cooking made them very tender.  The spices and stock were perfect.  Even my husband (who doesn't like onions) thought it was very good!!  All the taste of the original, but of course, healthier!!

Next time i'd skip the sugar on top. I even swapped out some red onions, yellow onions and shallots for some of the sweet onions. I also subbed out 1.5 cups of red wine for some of the beef stock. I also let it simmer for longer than the 30 min, i let it sit for 3.5 hours.

I liked the ease of the soup. I didn't like the cutting up of onions, that was a kick in the pants. Pretty sure my eyes continued to water long after i stopped cutting them. The other downside is that the onion soup smell stays in the house, even the day after.

The overall cost was probably more than a nice dinner with a side of french onion soup. But knowing what i put in the soup is nice to know.

For a 2 person household, i might also suggest cutting the recipe in half.

The fancy cheese on top gives it a nice earthy ton too. 

A good basic recipe. I thought using sweet onions and sugar made the end result a bit too sweet.. but the end result was still comforting on a cold, winter night.