For In-N-Out fans, here is a copycat Double-Double Animal-Style Cheeseburger recipe that you can make at home with a few simple ingredients you probably already have in your kitchen. With so many simple ingredients, the real star of the show is the sweet and tangy animal-style sauce, which is composed of mayo, whole-grain mustard, ketchup, and a few other basic add-ins.

1. For the Animal-Style Sauce:
   2 tablespoons whole-grain mustard
   1/2 cup mayonnaise
   1/2 cup ketchup
   1/4 cup diced pickles
   1 tablespoon red wine vinegar
   1 tablespoon sugar
   Pepper
   Salt
2. For the Onions:
   1 tablespoon olive oil
   1/2 white or yellow onion (sliced)
   Salt
3. For the Cheeseburger:
   1 white bread bun
   2 slices American cheese
   2 beef patties
   Lettuce leaves
   Sliced tomato
   Sliced pickles
   Pepper
   Salt

Directions

1. For the animal-style sauce, add the mayo, mustard, ketchup, red wine vinegar, sugar, and pickles to a medium-size mixing bowl.
2. Using a fork, whisk until thoroughly combined. Add salt and pepper to taste. Set aside.
3. In a pan on medium heat, add two beef patties. Season with salt and pepper while they cook for about five minutes on each side.
4. Once the patties are cooked, layer a slice of American cheese on top of each one. Cover the pan with a lid to trap in the heat and melt the cheese.
5. In a separate pan over medium heat, add some olive oil and your sliced onions.
6. Season the onions with salt, and stir frequently until the onions have caramelized slightly, about 10 minutes.
7. To build the sandwich, layer the sliced pickles, tomato, and lettuce on the bottom bun.
8. Stack a cheese-covered patty on top, and add a spoonful of animal-style sauce. Repeat with an additional patty and spoonful of sauce.
9. Top the finished burger with caramelized onions and a final bun. Enjoy!