French Onion Grilled Cheese

Cheese pull image of a caramelized onion grilled cheese sandwich

Get the Recipe: French Onion Grilled Cheese

This French onion grilled cheese sandwich is sloppy but worth it! It combines all the best things, beef stock, caramelized onions, fontina and gruyere cheeses, and buttery brioche bread.

5 from 2 ratings

Yield2 sandwiches

Prep15

Cook1 15

Total1 30

Ingredients

½ sweet onion
½ yellow onion
½ white onion
1 medium shallot
5 tablespoons unsalted butter
1 tablespoon beef fat/tallow
½ teaspoon kosher salt
¼ cup beef stock
¼ teaspoon marmite
2 cloves of roasted garlic
¼ teaspoon fresh ground black pepper
¼ teaspoon mushroom powder
1 teaspoon fresh thyme leaves
¼ teaspoon sherry vinegar
¾ cup fontina cheese
¾ cup gruyère cheese, (aged a minimum of 12 months)
4 slices brioche bread, (¾in or 2cm thick)

Equipment

knife
cutting board
Measuring spoons
measuring Cups
stainless steel sauté pan or enameled dutch oven
cheese grater
nonstick skillet or griddle
flat topped spatula

Print Recipe

Instructions

First, cut the top and bottoms off of your onions and then chop them in half. Lay the onion pieces flat-side down and make 1/4-1/2in (.6-1.2cm) slices all the way across. Don’t worry if they aren’t exactly even. It will all cook down by the end. Repeat this process with the shallot, but make finer slices (1/16-1/8in or .16-.3 cm)
Now that your alliums are sliced. Place your preferred cooking vessel on the stove top and turn the heat to medium-high. After the pan heats up a bit, add in 1 tablespoon (14g) of butter and the beef fat. Let that melt and begin to foam. Dump the sliced onions into your pan and toss them around in the fat. After a minute or so, sprinkle the salt over the onions and continue moving everything around in the pan, until the onions release their liquid and start turning translucent, this should only take between 5-7 minutes.
At this point, turn the heat down to medium, medium low heat. You do not want to unevenly cook the onions. This is all about browning (caramelizing) without burning or charring. Cook your onions, low and slow stirring every 5-10 minutes for the next 45 minutes. They will continue to lose liquid as they cook.
About 30 minutes into cooking the onions, take your cheese out of the refrigerator to sit at room temperature.
Also around this time, enough liquid will have evaporated that you can add in the beef stock and deglaze the pan a little bit. After adding the stock, stir in the marmite, roasted garlic, black pepper, and mushroom powder. Continue cooking the onions until the liquid has, again, mostly evaporated and they have turned a warm brown color.
Back to the onions. When done, the liquid surrounding the strands of onion will be creamy, like a thick gravy and the onions will be a deep brown. 2-3 minutes before taking the pan off the heat, mix in the thyme and the sherry vinegar. Set the pan aside and turn off the stove.
Next, prepare the rest of the ingredients for sandwich making. Grate the cheeses and mix them together into a pile. Butter your brioche slices, with the remaining butter, and setup your workstation. Place one slice of the brioche, butter side down, onto a medium-hot, non-stick pan. Take 1/4 of the cheese pile and spread it over the first piece of bread. Half of the onions get spread over the cheese, and then a second layer (another 1/4 of the pile) of cheese tops the onions. Add the second slice of brioche butter-side up and let it cook until you start to see some browning on the bottom slice of bread.
Flip the sandwich over and let the other side begin to crisp. Don’t worry about trying to perfectly brown each side in one flip, the first two turns are about making sure the cheese melts enough to fuse the whole grilled cheese sandwich together. Once you see the cheese melting, turn the heat up and then toast the outside of your sandwich to your preferred level of brown.
When you have reached a desired amount of toasting and melting, on your grilled cheese sandwich, plate it and make your second sandwich with the rest of the cheese and caramelized onions.
Slice and enjoy.

Notes

Make the onions up to 3 days ahead, for a quick dinner. It will only take about 10-15 minutes if the onions are ready to go
Keep in mind that your beef stock may be salty or not, depending on if you made homemade beef stock or purchased it at the store. Please salt to taste, when finishing. This will be especially important if you decide to double or triple the recipe.
If you want to make my homemade beef stock recipe on the same day as the grilled cheese sandwiches, you will need to add between 7-10 hours to your timeline. The stock can be made and refrigerated 4 days in advance before freezing. And will freeze up to 6 months.
If your heat is too high, you may need to deglaze the pan more than once to keep the onions from sticking. Try using a tablespoon (15ml) of stock at a time, if you need to stretch out the 1/4c (60ml) of stock. Pour it right where you see any burning onions and scrape gently to loosen them.
If you want an even crisper sandwich, you can spread more butter onto the toasting brioche as you flip. You can also spread mayo instead of butter on your brioche for more crisp and a little bit of tang.
If you want even more of a barrier between the onions and the bread, spread butter on the inside of the brioche as well.

Nutrition