In-N-Out Smash Burger Tacos with Secret Animal Sauce Step-by-step instructions

Before you start

Before starting, make the secret animal sauce by whisking together all the sauce ingredients in a small bowl; set aside.

Prepare the caramelized onions if you don't have them on hand—slowly cook sliced onions in a skillet with a bit of oil over medium-low heat until they are soft and browned.

Shred the iceberg lettuce and have all your ingredients within reach. Heat your griddle or cast-iron skillet over high heat for at least 5 minutes to ensure it's screaming hot for the perfect sear.

Instructions

Sauce and Prep

1. 1Make the Secret Animal Sauce
   In a medium bowl, combine the mayonnaise, ketchup, Dijon mustard, Worcestershire sauce, white vinegar, sweet pickle relish, 1/4 cup caramelized onions, garlic powder, and black pepper. Whisk until smooth and pink. Set aside.
   Look for The sauce is silky and pale pink, with bits of relish and onion evenly distributed.
   Tip Taste and adjust the seasoning—add a pinch of salt if needed.
2. 2Press the Beef onto Tortillas
   Divide the ground beef into 8 equal portions, about 2 tablespoons each. Place a portion onto a mini tortilla and press it firmly into an even layer that covers the surface, leaving a small border. Season lightly with salt.
   Look for The beef is thin and evenly spread, almost like a patty fused to the tortilla.
   Tip Wet your hands slightly to prevent the beef from sticking when pressing.

The sauce should be smooth and pink, with the relish and onions evenly distributed. The beef portions are ready, pressed onto the tortillas, and seasoned. The griddle is heating up. Everything is organized and within reach, so the cooking process will go quickly and smoothly.

Searing and Topping

3. 3Sear the Beef-Side Down
   Heat a griddle or large cast-iron skillet over high heat until smoking. Place the tortillas beef-side down on the hot surface. Cook for 4 minutes without moving, until the beef is deeply browned and crispy.
   Look for The beef is sizzling and the edges are caramelizing; the tortilla remains pliable.
   Safe temperature 160°F (71°C) internal temperature (ground meat)
   Tip Work in batches if needed; overcrowding lowers the heat and prevents crispiness.
4. 4Flip and Add Cheese
   Flip each tortilla so the beef side is up. Immediately place a slice of American cheddar on the hot beef. Cook for 1-2 minutes, until the cheese melts and becomes bubbly.
   Look for The cheese is fully melted and starting to bubble around the edges.
   Safe temperature 160°F (71°C) internal temperature (ground meat)
   Tip If the cheese isn't melting, cover the skillet with a lid for a few seconds.
5. 5Add Lettuce and Onions
   Pile a generous handful of shredded iceberg lettuce over the melted cheese, followed by a spoonful of the remaining caramelized onions.
   Look for The lettuce sits crisp and bright against the melted cheese and dark beef.
   Tip Keep the lettuce cold until ready to use for maximum crunch.
6. 6Drizzle with Secret Sauce
   Drizzle the secret animal sauce generously over the lettuce and onions, letting it cascade down the sides.
   Look for The sauce is thick and creamy, coating the toppings without dripping off.
   Tip Use a spoon or squeeze bottle for even distribution.

The beef is sizzling and browning, with crisp edges forming. After flipping, the cheese melts into a gooey layer over the beef. The lettuce adds a bright crunch, and the sauce is drizzled generously. The kitchen smells like a diner, and the tacos are almost ready to be folded.

Folding and Serving

7. 7Fold and Serve
   Carefully fold each taco in half, pressing gently to keep the filling inside. Serve immediately while hot and crispy.
   Look for The taco folds neatly, with melted cheese and sauce oozing slightly.
   Tip Fold with the beef side inward for the best bite.

The tacos fold neatly, with the filling staying inside. The tortillas are crispy and golden, the cheese is melted, and the sauce is creamy. Serve immediately to enjoy the full crunch and flavor.

Common mistakes

A common mistake is not heating the griddle enough—if the surface isn't smoking hot, the beef will steam instead of sear, resulting in a gray, soggy texture. Another pitfall is pressing the beef too thick; keep it thin and even for maximum crispiness.

Overcrowding the pan can also lower the temperature, so cook in batches if necessary. Finally, don't skip the sauce—it's the star that brings all the flavors together, so be generous when drizzling.

How to tell it’s done

The beef is done when it reaches an internal temperature of 160°F (71°C) and the edges are deeply browned and crispy. The cheese should be fully melted and bubbly, and the tortilla should be golden and crisp on the outside.

To check, lift a taco with a spatula—the bottom should be firm and browned, not soft or pale. If you're unsure, use an instant-read thermometer inserted into the beef patty to confirm the temperature.

• Ground meat: 160°F (71°C) in the thickest part