If you've ever scoped out The Chopping Block's blog, you may notice that there are quite a few pertaining to French onion soup. French onion soup is a classic traditional soup that is so comforting, and it's one of our Culinary Boot Camp students' favorite recipes that they learn during their five-day class.
You all have probably been out to dinner and ordered a crock of French onion soup with that deliciously rich, oniony, and beefy broth, a crispy crouton on top and melted Gruyere cheese oozing over the sides. I love this classic as is, but I really wanted to put my own twist on this traditional pairing. So, I decided to deconstruct this soup and turn it into a soup and sandwich combo reinventing this traditional favorite. Everyone loves the classic combo of grilled cheese and tomato soup so why not apply this concept to another soup fan favorite?
It all starts with the onions. Here I have cut my onion two different ways: one following the lines built into the onion and two cutting against the lines in the onion.
99% of the time when I'm teaching students how to slice or Julianne onions, I tell them to cut with the lines. The reason is that I want all the onion pieces s to be uniform in shape and size so they cook more evenly, and they look more esthetically pleasing. When you cut against the lines of the onion, you may have uneven shapes (think little rainbows), but you break apart the molecular construction of the onion, so they cook even faster. I also feel like the onions taste just a bit better for this soup preparation. If you want to learn more Knife Skills hacks, it's one of our most popular classes.
I decided to do a side-by-side comparison on both of these onions and how fast and evenly they caramelize and to determine whether there is any difference other than just looking different. You can see the onions on the left seem to be caramelizing more slowly and evenly throughout whereas the onions on the right seem to have some uneven more dark spots speckled throughout the onions.
I believe this is due to the uneven size as the smaller ones tend to brown a lot more quickly compared to the larger ones. This is, however, also dependent on how thick the onions are cut. There are also two different schools of thought on whether to salt your onions at the beginning or at the end of the caramelizing process. I tend to salt at the beginning because I like that the moisture is brought out and it helps to cook more evenly before browning too quickly. Some people tend to salt once the onions start to brown because they dislike the added moisture that comes out. To each their own! There is no right or wrong in this comparison just differing opinions… try them both for yourself.
I decided to keep these tester onions off to the side to be the filling for my grilled cheese sandwich. But as my new and improved version of French onion soup/grilled cheese starts to take form, I would highly recommend making the soup first and then strain out the onions to make the grilled cheese sandwich.
Let’s start with the sandwich part of this combo before I divulge my French onion soup recipe! It all starts with good quality bread. Today I used a sourdough, that I sliced myself, but other sliced bread will also be delicious! Gruyere cheese is the traditional topping for French onion soup but any melt-able cheese like provolone, mozzarella or even fontina would be delightful.
Now there is another debate when it comes to making grilled cheese sandwiches and that is: what do you put on your bread when you are griddling your grilled cheese? I am of the camp that I love smearing mayonnaise on my bread. The other alternative would be butter, but I find that when you use butter for a grilled cheese sandwich it tends to soak into the bread a little more. You can achieve crispiness, but I find sometimes it burns rather than becomes more crunchy. By using mayonnaise which is essentially just fat in eggs, you're staying more on the surface instead of soaking into the bread therefore creating this beautiful golden brown even crust you see here.
When I'm building my grilled cheese sandwich, I start by slathering the mayonnaise on one side of the bread and putting that down in a well-seasoned cast iron pan. I then add slices or shredded cheese evenly across the bread. I then put my caramelized onions in the center and top it with more cheese, followed by the last slice of bread that has been mayonnaised.
I choose to use a cast iron pan because I find that it really does create even heat for the perfect browning, but you could also use stainless steel if you don't have one. I leave the one side of the grilled cheese down for approximately 3 to 4 minutes depending on how fast it's browning and then I flip it over to crisp up the other side and to really melt the cheese. I do this over a medium heat to ensure a slow and low approach to crisping up your bread. I also like to cover my pan with a lid sometimes to make sure the cheese is melted all the way through. Or you can put your sandwich in a toaster oven, air fryer or regular oven to ensure full meltiness!
But what would an epic grilled cheese be without a soup to dip it in? When you are building your French onion soup to dip your epic grilled cheese into you want to first start by caramelizing your onions, like I discussed previously.
Keep cooking them until they're really dark and evenly golden brown before adding garlic to sauté for just about a minute. Just know that if while caramelizing your onions your pot gets a little too hot and you notice some uneven browning, don't be afraid to throw in a few splashes of water to help deglaze and cool down the pan. Once your garlic becomes aromatic, you're going to deglaze your pan with some Sherry, making sure to scrape the bottom of the pan to get all that delicious fond (brown bits on the bottom of your pan) off.
Then you'll add the flour. The flour bonds with the butter in the onions to help give us a little viscosity.
Once you've cooked the flour for about a minute or two then you are going to add the beef stock and fresh thyme. After the whole pot comes up to a complete boil, reduce the heat and simmer for approximately 20 minutes. I always like to finish my French onion soup with just a little shot of Worcestershire sauce. I find that it gives it a little rich umami flavor to cut through all the fattiness of the cheese in the Gruyere.
Now that you have built your French onion soup you can strain out the onions to be used in the center of your sandwich or you could also leave all the onions in the soup. I am a firm believer that sandwiches should always be cut diagonally! But here you have it - the ultimate French onion grilled cheese and soup dip combination.
I really hope you enjoyed this new and improved version of a classic French onion soup. You should check out our Culinary Boot Camp where on the third day you get to make this soup and learn many other soup techniques. If you want to learn other classic dishes, it is the epitome of every cooking technique you could need as a home cook.