The Hidden Trick for Fast Food-Style Smash Burgers (Spoiler: You Probably Have It Right Now)

Summer's here, and that means it's time to fire up the grill! But this year, everyone's raving about smash burgers. From the viral Smash Burger Tacos to the trending onion-packed Oklahoma Burger, smash burgers are taking over social media. Whether it's the rise of griddles or our craving for recreating fast food favorites at home, one thing's for sure—they're insanely tasty.

With their juicy centers and crispy, lace-like edges, smash burgers are hard to beat. Our team can't get enough of this style, always hunting for new tips, tools, and tricks to elevate them. Well, I just discovered the ultimate hack for making fast food-style smash burgers—and the best part? You probably have everything you need to do it right now. And it all begins with In-N-Out.

The Secret to In-N-Out’s Smash Burger Magic

When recreating a fast food experience at home, it’s smart to start with the originals. After all, imitation is the highest form of flattery, right? For me, In-N-Out is the ultimate fast food burger—this cult-favorite California chain is famous for its Animal-Style burgers and fries, a secret (but not-so-secret) menu that has become an icon in its own right.

What sets the Animal-Style Burger apart from the rest? It all comes down to a secret sauce (or 'spread' at In-N-Out), which is essentially a twist on Thousand Island Dressing. But that’s not all—grilled onions are part of the magic, along with the little-known detail on the In-N-Out website: a ‘mustard-cooked beef patty.’

That's right. The key to creating the best smash burgers is simply yellow mustard. But the real trick is knowing exactly when—and how—to add it to your patties.

How to Recreate Animal-Style Burgers at Home

At In-N-Out, the burger patties are placed on a hot flat-top griddle, where a teaspoon or two of yellow mustard is spread on the uncooked side just before flipping. As the mustard caramelizes on the griddle, it softens the sharp tang and forms an even crispier crust as the patties are smashed. It's a beautiful thing to watch.

The sweet, caramelized onions and the secret 'spread' add a touch of sweetness to the burger, while the mustard-griddled patty delivers a rich, savory flavor with a subtle mustard kick at the finish. When paired with fresh lettuce, pickles, and a soft bun, it creates the perfect burger harmony. No wonder In-N-Out has such a loyal following.

Don’t live near an In-N-Out? No worries! This simple trick can easily be recreated at home for your own smash burger adventures. All you really need is yellow mustard, though I’d argue that caramelized onions are a must for the full experience. Even better, we have a Copycat Animal-Style Burger recipe on Dinogo, so you can make a perfect replica right in your kitchen. Happy smashing!