Quick Recipe Version (TL;DR)
Quick Ingredients
- 2 large yellow onions, thinly sliced (about 4 cups)
- 1 tablespoon unsalted butter + 1 tablespoon neutral oil (for onions)
- 1/2 teaspoon kosher salt (for onions)
- 1/3 cup mayonnaise
- 2 tablespoons ketchup
- 1 tablespoon sweet pickle relish
- 1 teaspoon white vinegar
- 1/2 teaspoon granulated sugar
- 1/4 teaspoon fine salt + 1/8 teaspoon black pepper
- 2 hamburger buns
- 2 teaspoons yellow mustard
- 2 tablespoons unsalted butter, softened (for toasting buns)
- 4 slices American cheese
- 8 dill pickle chips
- 1 medium tomato, sliced (4 slices)
- 2 crisp iceberg lettuce leaves
Do This
- 1. Caramelize onions in butter + oil with salt over medium-low heat, 25–30 minutes; keep warm.
- 2. Stir together the spread (mayo, ketchup, relish, vinegar, sugar, salt, pepper); chill while you cook.
- 3. Heat a skillet/griddle over medium (about 350°F surface temp) and butter the outside of each bun half.
- 4. Lightly smear mustard on the cut sides of the buns; toast cut-side down so the mustard griddles, 1–2 minutes.
- 5. Flip buns butter-side down to brown the outside, 1–2 minutes; set aside.
- 6. Assemble in the warm pan: bun, cheese, big pile of onions, pickles, tomato, lettuce, spread, top bun.
- 7. Grill 1–2 minutes per side, covered, until deep golden and the American cheese is fully melted.
Why You’ll Love This Recipe
- All the classic “Animal Style” vibes, but in a home-cook-friendly grilled cheese format.
- Griddled mustard + buttery toasted bun adds the signature tangy, savory edge.
- A generous heap of caramelized onions makes it sweet, jammy, and restaurant-level satisfying.
- The copycat spread is quick to stir together and tastes shockingly close.
Grocery List
- Produce: 2 large yellow onions, 1 medium tomato, iceberg lettuce, dill pickles (chips)
- Dairy: unsalted butter, American cheese slices, mayonnaise
- Pantry: neutral oil (canola/vegetable), ketchup, sweet pickle relish, yellow mustard, white vinegar, sugar, salt, black pepper
Full Ingredients
Copycat Spread (makes about 1/2 cup; you’ll use about 6 tablespoons)
- 1/3 cup mayonnaise
- 2 tablespoons ketchup
- 1 tablespoon sweet pickle relish
- 1 teaspoon white vinegar
- 1/2 teaspoon granulated sugar
- 1/4 teaspoon fine salt
- 1/8 teaspoon freshly ground black pepper
Caramelized Onions
- 2 large yellow onions, thinly sliced (about 4 cups)
- 1 tablespoon unsalted butter
- 1 tablespoon neutral oil (canola or vegetable)
- 1/2 teaspoon kosher salt
- 2 tablespoons water (as needed, to deglaze if onions start sticking)
Sandwiches
- 2 hamburger buns (soft, standard-size)
- 2 tablespoons unsalted butter, softened (for toasting buns)
- 2 teaspoons yellow mustard (about 1 teaspoon per sandwich)
- 4 slices American cheese
- 8 dill pickle chips
- 1 medium tomato, sliced into 4 slices
- 2 iceberg lettuce leaves (crisp, dry)
Step-by-Step Instructions
Step 1: Make the spread
In a small bowl, stir together the mayonnaise, ketchup, sweet pickle relish, white vinegar, sugar, salt, and black pepper until smooth and evenly mixed.
Cover and refrigerate while you cook the onions and toast the buns. (Even 15–20 minutes of chilling helps the flavors meld.)
Step 2: Caramelize the onions low and slow
Heat a large skillet (cast iron or stainless steel works great) over medium-low heat for 2 minutes. Add the butter and oil.
Add the sliced onions and toss to coat. Sprinkle with the kosher salt. Cook, stirring every 2–3 minutes, until the onions become deeply golden-brown and jammy, 25–30 minutes.
If the onions begin sticking or browning too quickly at any point, add 1 tablespoon water and scrape up the browned bits. Keep cooking until the water evaporates and the onions soften again.
Step 3: Keep onions warm while you toast
Transfer the finished onions to a bowl and cover loosely with foil, or push them to one side of the skillet over low heat to keep warm. Wipe the skillet/griddle lightly if there are lots of dark onion bits.
Step 4: Prep the buns with butter and mustard
Split the hamburger buns if they’re not already cut. Spread about 1/2 tablespoon softened butter on the outside of each bun half (the rounded tops and the bottoms).
Then spread a thin, even layer of yellow mustard on the cut sides of the buns (about 1/2 teaspoon per cut side). This is what gives you that signature “mustard-griddled” flavor.
Step 5: Toast and griddle the buns
Heat a clean skillet or flat griddle over medium heat until hot, about 350°F surface temperature (or until a drop of water sizzles and evaporates quickly).
Place the buns cut-side down (mustard-side down) and toast until lightly golden and fragrant, 1–2 minutes.
Flip and toast the buttered outside until golden, 1–2 minutes. Transfer buns to a plate.
Step 6: Build the Animal Style grilled cheese
Lower heat to medium-low. Place the bottom bun halves (one per sandwich) back on the skillet.
Layer each sandwich in this order for the most “In-N-Out-style” bite:
- Bottom bun
- 1 slice American cheese
- A big heap of caramelized onions (about 1/2 cup per sandwich)
- Pickles (4 chips per sandwich)
- Tomato (2 slices per sandwich)
- Lettuce (1 leaf per sandwich)
- Spread (about 1 1/2 tablespoons per sandwich, on the underside of the top bun)
- Top bun
Add the second slice of American cheese if you like it extra melty: you can tuck it right on top of the onions before the pickles.
Step 7: Griddle until melty and deeply golden
Cook the sandwiches over medium-low heat until the bottom is crisp and golden, 1–2 minutes. Carefully flip.
Cover the skillet with a lid (or tent loosely with foil) and cook another 1–2 minutes, until the cheese is fully melted and the bun is deeply toasted.
Transfer to a cutting board, rest for 1 minute, then slice in half and serve immediately.
Pro Tips
- Go low on the onions: If your heat is too high, they’ll scorch before turning sweet and jammy. Medium-low with steady stirring is the move.
- Dry your lettuce and tomato: Pat them with paper towels so the sandwich stays crisp instead of soggy.
- Cover to melt: A lid traps heat and melts American cheese quickly without over-toasting the buns.
- Mustard goes on the cut side: Butter toasts the outside; mustard griddles on the inside for that classic tang.
- Use American cheese slices: It melts into that smooth, nostalgic layer that makes this sandwich feel like the real thing.
Variations
- Extra “Animal Style” onions: Add a second onion (3 total) and pile them high for a more over-the-top, diner-style build.
- Spicy version: Add 1 teaspoon chopped pickled jalapeños to the spread and use pepper jack in place of one American slice.
- Protein add-on (not a grilled cheese anymore, but delicious): Add 2 thin beef patties (2–3 oz each) or a smashed veggie patty and proceed as written.
Storage & Make-Ahead
For the best texture, this sandwich is meant to be eaten right away. That said, you can make components ahead:
- Spread: Refrigerate in an airtight container for up to 5 days.
- Caramelized onions: Refrigerate for up to 4 days. Rewarm in a skillet over medium-low heat with 1–2 teaspoons water until steamy.
- Assembled sandwich: If you must store leftovers, wrap and refrigerate up to 1 day. Reheat in a skillet over medium-low about 2–3 minutes per side (cover to re-melt cheese). Expect softer lettuce; you can remove and add fresh after reheating.
Nutrition (per serving)
Approximate, per 1 sandwich: Calories: 690; Protein: 16 g; Carbohydrates: 54 g; Fat: 46 g; Saturated Fat: 18 g; Fiber: 4 g; Sugars: 14 g; Sodium: 1450 mg.
