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Impress your guests with Smashburgers with Special Truffle Sauce, which are topped with Gruyère cheese, arugula, and caramelized onions. I love making these burgers for an elevated twist on the fast food classic.
Although there are a few components to these burgers, you can make both the sauce and caramelized onions in advance for easy hosting. The homemade truffle sauce made with mayo, Dijon mustard, chopped cornichons, lemon, and truffle oil makes the most epic special sauce for this burger.
There are a few specialty ingredients that you’ll need to grab from the store, but I promise it’s worth it. I recommend using 85% lean ground beef, which has a high enough fat content that the burgers will be flavorful and juicy, even when they’re smashed thin. For the cheese, I like to use a sharp, nutty cheese like Gruyère, but Swiss or white cheddar will work too. The black truffle oil adds rich, umami notes to the sauce; a little oil goes a long way so you can use the rest in some of my other favorite truffle recipes on the blog, like my Bibb Lettuce Salad with Black Truffle Vinaigrette and Mimolette.
ingredients:
- Mayonnaise
- Cornichons
- Dijon Mustard
- Lemon Juice
- Black Truffle Oil
- Kosher Salt
- Freshly Ground Black Pepper
- Extra-Virgin Olive Oil
- Yellow Onions
- Ground Beef
- Unsalted Butter
- Brioche Buns
- Gruyère Cheese
- Baby Arugula
step-by-step:
step one: make the truffle sauce
In a small bowl, combine the mayonnaise, cornichons, mustard, lemon juice, and truffle oil. Season with salt and pepper to taste. Cover and refrigerate until ready to use.
step two: make the caramelized onions
Heat 1 to 2 tablespoons oil in a large skillet set over medium heat. Add the onions and a pinch of salt. Cook, stirring often, for 30 to 40 minutes until deeply golden and caramelized. Reduce the heat if they brown too quickly. Set aside.
step three: form and cook the burgers
Divide the ground beef into 12 equal portions (2½ to 3 ounces each) and roll into loose balls.
Heat a large cast-iron skillet or griddle over medium-high heat until very hot. Working in batches, place 2 to 3 beef balls in the skillet. Immediately smash each with a heavy spatula or burger press until very thin. Season with salt and pepper.
Cook for 2 to 3 minutes or until the edges are crispy and browned. Flip, top with a slice of cheese, and cook for 1 to 2 minutes, or until the cheese is melted and the patties are cooked through. Transfer to a plate and repeat with rthe emaining patties.
step four: toast the buns
Lightly butter the brioche buns (optional) and toast, cut-side down, in the skillet until golden brown.
step five: assemble the burgers
Spread a generous spoonful of truffle sauce on the bottom bun. Top with a handful of baby arugula, two cheesy burgers, and a spoonful of caramelized onions. Top with the halved bun and secure with a cornichon and toothpick. Repeat with the remaining burgers.
recipe faqs:
Yes! You can make the truffle sauce up to five days in advance. Store in an airtight container in the refrigerator until you’re ready to use it.
Unlike traditional burgers, smashburgers are flattened into thin patties, which become charred when cooked on a hot griddle or cast-iron pan. The patties are cooked with cheese and caramelized onions and stacked high to create one delicious bite.
Next time you’re craving a juicy burger, try this recipe for Smashburgers with Special Truffle Sauce. Comment below and let me know how it comes out!
Looking for more burger recipes? Try these!
Blue Cheese and Balsamic Burger Salad
Greek-Inspired Grilled Lamb Burgers
Juicy Indoor Burgers with Burger Sauce
Smashburgers with Special Truffle Sauce
Ingredients
Special Truffle Sauce:
- 1/2 cup mayonnaise
- 1/4 cup finely chopped cornichons
- 1 tablespoon Dijon mustard
- 1 tablespoon freshly squeezed lemon juice
- 1 tablespoon black truffle oil
- kosher salt, to taste
- freshly ground black pepper, to taste
For the Caramelized Onions
- 1-2 tablespoons extra virgin olive oil
- 2 yellow onions, thinly sliced
- Pinch of kosher salt
For the Burgers:
- 2 pounds ground beef (85/15)
- Kosher salt, to taste
- freshly ground black pepper, to taste
- unsalted butter (optional)
- 6 brioche buns, sliced
- 12 slices Gruyère, Swiss, or white cheddar cheese
For serving:
- baby arugula
- cornichons
Instructions
Make the Truffle Sauce:
- In a small bowl, combine the mayonnaise, cornichons, mustard, lemon juice, and truffle oil. Season with salt and pepper to taste. Cover and refrigerate until ready to use.
Prepare the Caramelized Onions:
- Heat 1 to 2 tablespoons oil in a large skillet set over medium heat. Add the onions and a pinch of salt. Cook, stirring often, for 30 to 40 minutes until deeply golden and caramelized. Reduce the heat if they brown too quickly. Set aside.
Form and Cook the Burgers:
- Divide the ground beef into 12 equal portions (2½ to 3 ounces each) and roll into loose balls.
- Heat a large cast iron skillet or griddle over medium-high heat until very hot. Working in batches, place 2 to 3 beef balls in the skillet. Immediately smash each with a heavy spatula or burger press until very thin. Season with salt and pepper.
- Cook for 2 to 3 minutes or until the edges are crispy and browned. Flip, top with a slice of cheese, and cook for 1 to 2 minutes, or until the cheese is melted and the patties are cooked through. Transfer to a plate and repeat with remaining patties.
Toast the Buns:
- Lightly butter the brioche buns (optional) and toast cut-side down in the skillet until golden brown.
Assemble the Burgers:
- Spread a generous spoonful of truffle sauce on the bottom bun. Top with a handful of baby arugula, two cheesy burgers, and a spoonful of caramelized onions. Top with the halved bun and secure with a cornichon and toothpick. Repeat with remaining burgers.
Nutrition information is automatically calculated, so should only be used as an approximation.
Photography and styling by Eat Love Eats.
Both my husband and I agree—best burger I’ve ever had!! Can’t wait to make this again
The sauce on this burger is incredible! Such an easy quick dinner, thank you so much Alex!
I swear I could eat the sauce by the spoonful ha!
WOW! 10/10! One of the best burgers I have ever had! Thank you so much!!!!!
Just made these burgers and the truffle mayo, caramelized onions and arugula take a simple burger over the top to fabulousness. This will be a new regular in our household. Your recipes are where I go for amazing dinners. Thanks!
Top Notch! These were seriously delicious. Thanks so much for this recipe! I can’t wait to make it again. Yum!
This sounds amazing! Would you please post a link to the truffle oil you use?
Hello! These look incredible 🤤 Where does one buy black truffle oil? Is there a specific brand you prefer? Thank you!! Your recipes never disappoint!
It’s usually in the oil/vinegar section! I try to buy one in the smallest bottle- because you only need a little to go a long way! Truff is great, but most black truffle oils are pretty delish.