Animal Style is In-N-Out’s open secret: a beef patty cooked with mustard pressed into the griddle, topped with slow-caramelized onions, American cheese, pickles, and a mayo-ketchup-relish spread. It’s worth making at home because the spread and the onions both keep well in the fridge for days, which means the second and third burgers of the week take about five minutes to put together.
The short version of why this works
Two things actually drive this recipe. First, the mustard-on-the-griddle move: you press a thin layer of yellow mustard directly onto the raw side of the patty before it hits the hot surface, and the heat caramelizes the mustard into the crust. You get a tangy, slightly sharp edge that cuts through the richness of the cheese and onions. Without it, the burger is just a cheeseburger with a good sauce. Second, the onions need real time — at least 45 minutes over low heat with a splash of water added whenever they threaten to stick. Rush them and you get soft onions. Give them time and you get something jammy and sweet that holds its own against every other component. Both of these can be done well ahead of serving, which is exactly the point.
Ingredient notes
- Ground beef (80/20): The fat content matters here. Leaner beef will dry out on a hot griddle, especially with mustard pulling moisture from the surface. Stick with 80/20.
- Yellow mustard: Use standard American yellow mustard, not Dijon or spicy brown. The milder flavor is what caramelizes correctly without turning bitter.
- American cheese: Processed American cheese slices — the individually wrapped kind — melt faster and more evenly than any natural cheese. That uniform melt is part of what makes this work. Skip the cheddar here.
- Sweet pickle relish: This goes into the spread, not on the burger separately. If you only have dill relish, add a small pinch of sugar to compensate.
- Iceberg lettuce: It’s the right call for this burger. It stays crisp and doesn’t wilt under warm components the way softer greens do.
Troubleshooting
- The mustard burns before the patty is cooked through: Your griddle is too hot. Mustard scorches fast. Medium to medium-high heat is enough — you want a sizzle, not smoke. If the mustard side is darkening too quickly, flip earlier and finish on the non-mustard side.
- The spread tastes flat after refrigerating: Cold dulls acidity. Stir in a few extra drops of white vinegar and taste again before using. The spread is fine refrigerated for up to five days, but always re-season cold.
- The caramelized onions are browning unevenly: The pan is too hot or too dry. Keep the heat low and add water a tablespoon at a time whenever the onions start sticking. Stirring every few minutes also helps them cook evenly.
- The bun goes soggy fast: Toast the cut sides until they’re genuinely golden — pale toasting doesn’t create enough of a barrier. Also, spread the sauce on both the top and bottom bun rather than pooling it all in one spot.
- The patty is cooked through but tastes dry: It was likely overworked when shaped. Handle the beef as little as possible — press it into a patty once and stop. Skip the egg in the mix — it makes the patty mushy and encourages overworking the meat.
In-N-Out Animal Style Burger
Ingredients
For the Animal Style Spread:
- ½ cup mayonnaise use high-quality mayo for best flavor
- 2 tablespoons ketchup
- 1 tablespoon sweet pickle relish
- 1 teaspoon white vinegar
- ¼ teaspoon sugar
For the Caramelized Onions:
- 2 tablespoons unsalted butter
- 2 cups yellow onions, finely diced about 2 medium onions
- ¼ teaspoon kosher salt
For the Burgers:
- 1 ½ pounds ground beef (80% lean) divide into 4 equal patties
- 1 teaspoon vegetable oil
- 4 pieces Hamburger buns preferably brioche or classic aged white buns
- 4 tablespoons yellow mustard one tablespoon per patty
- 4 slices American cheese use deli-style for better melt
- 1 cup iceberg lettuce shredded
- 1 medium tomato sliced into 8 thin rounds
- 12 slices dill pickles or more to taste
Instructions
- Make the Animal Style Spread: In a small bowl, combine mayonnaise, ketchup, sweet pickle relish, vinegar, and sugar. Mix thoroughly and refrigerate until ready to use. This allows the flavors to meld.
- Caramelize the Onions: In a skillet over medium-low heat (300°F / 150°C), melt butter. Add diced onions and salt. Stir frequently for 15–20 minutes until deeply golden brown and incredibly soft. Reduce heat if they begin to brown too fast—they should be sweet and jammy, not crispy.
- Prepare the Patties: Divide ground beef into 4 equal balls and flatten into thin, wide patties. Season lightly with salt. Heat a cast iron skillet or griddle to medium-high (400°F / 200°C), add vegetable oil, and sear each patty.
- Mustard Grill Your Patty: Once the first side has seared (about 2-3 minutes), flip and immediately spread 1 tablespoon of yellow mustard on the cooked side. Continue cooking another 1-2 minutes, then top each with a slice of cheese until melted.
- Toast the Buns: Lightly toast hamburger buns, cut side down, in a clean pan or on the griddle for 1–2 minutes until golden.
- Assemble the Burger: Spread a generous spoonful of Animal Style spread on both bun halves. Layer with shredded lettuce, tomatoes, pickles, the cheesy mustard-seared patty, and caramelized onions. Cap with the top bun and serve hot.
Notes
- For a keto version, serve the burger in lettuce wraps instead of buns.
- Use American cheese for authenticity, but cheddar works if you want a sharper flavor.
- Add grilled jalapeños for a spicy variation.
- Onions can be made a day ahead and refrigerated—just reheat gently before serving.
Nutrition
FAQ
Can I make the caramelized onions ahead of time?
Yes, and it’s the best way to do it. Cooked onions keep in an airtight container in the fridge for up to five days. Reheat a portion in a small pan with a splash of water before building each burger.
What internal temperature should the beef patties reach?
Cook ground beef patties to 160°F (71°C) internal temperature — no exceptions for ground beef. Use an instant-read thermometer; the mustard crust can make the outside look done before the inside is safe.
How long does the Animal Style spread keep in the fridge?
Up to five days in a sealed jar or container. Give it a stir before each use, and taste it — you may want a small splash of vinegar to brighten it back up after a couple of days.
Can I cook the patties on an outdoor grill instead of a flat griddle?
You can, but the mustard technique works better on a flat surface. On grill grates, the mustard drips off before it can caramelize into the crust. A cast iron skillet or flat griddle pan on the grill grates is a good workaround.
Can I freeze the cooked patties for later in the week?
Yes. Cook the patties fully to 160°F, let them cool, then freeze individually on a baking sheet before transferring to a bag. Reheat in a covered skillet over medium-low with a tablespoon of water to keep them from drying out.
What if I can’t find soft white hamburger buns — will brioche work?
Brioche works fine as long as you toast it well. It’s slightly richer and sweeter than a standard white bun, which can tip the balance a little, but it holds up to the sauce without falling apart.