The In-N-Out Secret Menu Hack You Should Use On All Your Burgers

American fast food chain In-n-Out Burger has held a soft spot in the hearts of casual diners and professional chefs alike since the first location opened in 1948. Over the years, In-n-Out Burger has maintained its reputation for consistently better-than-average fast food fare. From the toasted hamburger buns and the fresh iceberg lettuce, to the melty American cheese and high-quality beef patties, their core menu always delivers the goods.

In-n-Out veterans know that while the core menu is great, it can be made so much greater by taking advantage of their not-so secret menu. This includes options of getting your burger in a lettuce wrap instead of a bun ("protein style") or quadrupling your burger patties ("4x4"), but it also offers an option to get your burger "mustard-grilled." If you like to get your In-n-Out burgers served "animal style" with grilled onions and extra sauce, you'll be familiar with this process.

When you order a mustard-grilled burger, the cook will add a bit of mustard to your patty before flipping it on the grill. It's a great way to add some additional flavor to any of your favorite In-n-Out burger options, and here's why you'll never go back once you give it a go.

Adding mustard to a burger has been a convention ever since the burger's inception. The acidic tang of this singular condiment pairs nicely with the natural flavors of beef, so it makes sense that it would find a home on a burger. As burger restaurants have evolved, mustard is still a heavy player on the scene. It was only a matter of time before inventive burger chefs tried slathering a patty in mustard during the grilling process, and it's something that burger aficionados swear by.

The process of mustard-grilling a burger is relatively simple. You throw your patty on the grill, squirt a bit of mustard on the face-up side, and then give it a flip to finish the patty off. While the burger cooks, the mustard caramelizes and imparts its flavor into the patty itself. Even if you haven't explored all the flavorful options mustard has to offer, the textural value add alone is worth adding mustard to the grilling process.

In addition to adding a thin, crispy layer of texture to the burger patty, the sharp mustard flavor transforms in the grilling process. The meat absorbs a lot of the stronger flavors, leaving only a nice hint of mustard acidity on the palate. Once you try it out, you'll be asking for mustard-grilled burgers every time you roll through an In-n-Out drive-thru.

While the good folks at In-n-Out will be happy to whip up a mustard-grilled burger for you, it's easy enough for home grillers to take advantage. In-n-Out uses a flat-top grill, which distributes heat evenly to the mustard-coated burger patty, which creates a likewise even distribution of mustard flavor to the burger. Outdoor grillers can still use this technique, though they'll likely want to use a brush to spread the mustard evenly across the patty.

Home cooks can also take advantage of the wide variety of mustards that are available to them. In-n-Out uses classic yellow mustard, which is a great jumping-off point, but who's to stop home cooks from imparting a little sweetness from their favorite honey mustard? Or how about mixing that fancy stuff packed with mustard seeds into your ground beef before it hits the grill? With so many different types of acidic condiments at your disposal, it's only a matter of time before you discover the next great burger innovation.