I love grilling at the end of summer and into the fall. These French Onion Burgers definitely have a fall feel to them. Each juicy burger is topped with slow-cooked caramelized onions and melted Gruyere cheese served up on a buttery toasted brioche bun with a thick slice of garden fresh tomato, a handful of arugula, and homemade herbed aioli. It sounds like something you’d order in a restaurant, right? So fancy! But it’s easy to put together and would be great to serve for a fall BBQ party or anytime you’re in the mood for a burger that will knock your socks off.
It’s important to start with really good ground beef. The most important part is that you want the beef to be marbled with extra fat because that translates to juicy burgers. Using 80% lean ground beef means that you will lose quite a bit of the volume and shrink a lot during cooking due to the extra fat rendering off. So when I’m making burgers, I tend to go with a little higher weight per burger, between 5-6 ounces of meat per burger. If you decide to use leaner beef, you can get away with 4-5 ounces per burger.
I don’t season the meat with much more than sea salt, freshly ground black pepper, and a little garlic powder. One more tip: get the meat from the butcher counter if possible. The beef in those little 1 lb. packages is handy, but I find that it makes for tougher burgers because it’s been handled more, and the beef is always fresher from the butcher counter.
I’m getting ahead of myself – we need to talk about caramelized onions!
Caramelized onions are like candy to me. And I can’t think of many dinner, side dish, appetizers, or salad recipes that wouldn’t be enhanced with a spoonful of caramelized onions.
Making caramelized onions is super easy. You can use a Dutch oven, large pot, or slow cooker. My recipe for these burgers adds a few extra ingredients because it’s based on French Onion Soup. But it’s still one of those “put it on the stove and forget about it” kind of things. You can use any variety of onion, or a combination. I try to use about half sweet onions, like Vidalia, and the rest a combo of red, yellow, and white. Funny enough, some onions are better or milder when cooked, and others are better suited to eat raw. (Kind of like apples!) Having a good mix is fun, but you can also use just regular yellow onions.
I like using my Dutch oven over low heat. It takes nearly two hours, maybe a bit longer, for these onions to cook down and turn deep amber in color. I’ve also put them into the same Dutch oven in my oven and cooked them slowly all day long at 300°F. Low and slow is the best way, whatever method you use.
Because these burgers are French Onion Burgers, I add beef broth to the pot to help the onions soften. The broth condenses and mingles with the sweet caramel flavor of the onions and really, this is the stuff of dreams. I also add a little pinch of thyme – fresh or dried is fine. Give the onions a stir every so often, but for the first 3/4 of the cooking time, the mixture will look kind of soupy. Then the liquid will continue to evaporate, the bottom of the pan will start to brown, and then you’ll need to check them a little more often to prevent any burning.
Five pounds of onions yields about 2 cups caramelized onions. You’d think that would last a long time, but you’ll be smearing them on everything you can think of. Grilled cheese, anyone? Once the onions are done, keep them refrigerated until you’re ready to cook the burgers. The caramelized onions will keep for quite a long time in the fridge, so you can even make them in advance. (Or if you’re like me, you’ll always want some in the fridge.)
The Herbed Aioli can also be prepped in advance. It will keep for about a week. Now, it does make a lot of aioli. If you’d rather just revamp store-bought mayo, by all means do it. I’m all for shortcuts like that. Just stir in fresh herbs to taste and add some minced fresh garlic. I feel like the aioli and the beef broth in the onions is what really makes this burger special. It’s just that extra bit of flavor that takes it up a few dozen notches. :)
And of course, what would a burger be without a pile of fries?
French Onion Burgers Recipe
4 tablespoons butter
5 pounds onions, any variety (I use a 50/50 mix of sweet and yellow, red, and/or white onions)
1 cup flavorful beef broth
Big pinch fresh or dried thyme leaves
Sea salt, to taste
For the burgers:
3 pounds good quality 80% lean ground beef
Sea salt and freshly ground black pepper, to taste
8 ounces Swiss cheese, shredded or sliced (can use Gruyere, Jarlsberg, or Emmentaler)
2 tablespoons butter (optional)
8 brioche hamburger buns
Two large ripe heirloom or other variety garden tomatoes
2-3 cups baby arugula
Herbed Aioli (recipe follows)
Potato fries, for serving
1. Prepare the caramelized onions first. Cut onions into 1/4″ to 1/2″ thick rounds.
2. Melt the butter in a large Dutch oven. Add half of the onions. Cook, stirring and turning them over often. As they lose volume, add more of the onions until they are all in the pot. Turn heat to low and cover pan. Allow to cook for 2-3 hours on low, checking every half hour or so and stirring so they don’t burn on the bottom of the pan. (They probably won’t burn at the low temp, but it’s good to check anyway.)
3. When the onions have lost about 25% of their volume, remove the lid and pour the beef broth over the onions. Add the thyme, and season with a little sea salt. Stir well. Bring temperature up a bit and cook without the lid for another 30-45 minutes, or until the liquid has evaporated and the onions have become almost jam-like. Remove from heat. Transfer to a jar with tight-fitting lid. Let cool 20-30 minutes, then refrigerate until ready to use.
4. For burgers, preheat a BBQ grill or an indoor grill pan or large cast-iron skillet. Divide the beef into 8 equal balls. Form into large patties about 5″ in diameter. Press a little indentation in the center so the burgers will cook evenly. Season each side of the burgers with a little sea salt, black pepper, and garlic powder.
5. Cook burgers for 3-4 minutes on the first side, then flip and continue cooking for another 5-6 minutes, or until cooked through and juices run clear.
6. While burgers are still on the heat, spoon a heaping 1 1/2 tablespoons of the caramelized onions onto each of the burgers, working in batches if needed. Top each one with 1 ounce of grated or sliced cheese. Cover and allow the cheese to melt. (If you’re cooking indoors, you can also place the cheese- and onion-topped burgers on a pan and broil for 1-2 minutes on high.)
7. If desired, spread a little butter onto each of the cut sides of the brioche buns and toast them briefly in a clean pan or on the grill, depending on which you’re using. Transfer to a platter until ready to serve.
8. To serve, place the burgers on the bottom buns. Top with a thick slice of tomato and a handful of the arugula. Spread some of the aioli on the top bun and place on the burger. Serve immediately.
Herbed Aioli Recipe
adapted from Martha Stewart
1 large whole egg*
1 teaspoon lemon juice
1 teaspoon Dijon mustard
1 garlic clove
¼ to ½ teaspoon salt (to taste)
½ cup avocado, canola or grape seed oil (or another flavorless oil)
½ cup extra virgin olive oil
2 Tablespoons fresh sage, finely minced
2 sprigs fresh rosemary, needles only, finely minced
2 sprigs fresh thyme, leaves only
In a blender or food processor, combine whole egg, lemon juice, mustard, garlic, and a little salt. Pulse until combined. With the motor running, pour the canola oil through the feed hole in a slow drizzle, followed by the olive oil, also in a slow drizzle. The mayonnaise will start to thicken and you’ll hear the sound change. That’s when you’ll know it’s time to turn off the blender. Scrape down the sides and add the thyme. Pulse a few times until everything is combined. Transfer to a bowl, cover and chill until ready to serve.
*This recipe contains raw egg. Caution should be used when consuming raw eggs, particularly when serving to children, the elderly, pregnant women and those with weakened immune systems. I’ve never gotten sick from raw eggs, but I know of people who have. Make sure to use very fresh eggs and wash the outside of the egg before cracking it, or use pasteurized eggs.
To make the aioli with prepared mayonnaise, stir together 1/2 cup mayo with 1/2 teaspoon Dijon mustard, 1 garlic clove (minced), a pinch of salt, a little apple cider vinegar or fresh lemon juice, and 1 tablespoon fresh sage, 1 fresh rosemary sprig finely minced, and one sprig fresh thyme (leaves only). Cover and refrigerate until ready to use.