In-N-Out Style Double Smash Burger

Ingredients

Ingredient notes & substitutions

80/20 ground beef:

The higher fat content is non-negotiable here — it's what keeps the thin smashed patties juicy instead of dry and crumbly.

American cheese:

Skip sharp cheddar or Swiss; American melts into that signature gooey, glue-like layer that fuses the two patties together.

Mayonnaise, ketchup and relish:

This trio is the backbone of the copycat spread — use sweet relish, not dill, to get the right balance of tang and sweetness.

Caramelized onions:

The recipe uses them two ways (in the sauce and as a topping), so make a big batch ahead to save yourself a step on burger night.

Soft hamburger buns:

A standard supermarket potato or sesame bun works great — just make sure it's soft enough to squish, since sturdy artisan buns fight the smash burger vibe.

White vinegar or pickle juice:

This is the secret sour note in the sauce; pickle juice adds a little extra brine if you have a jar open already.

Method

1. 1

   Combine all the sauce ingredients until smooth, cover, and refrigerate at least 30 minutes so the flavors meld.

   
2. 2

   Divide the beef into 2–3 oz portions and form loose balls — don't season until they hit the pan.

3. 3

   Heat a griddle or heavy skillet over high heat and lightly oil it.

4. 4

   Place the beef balls on the hot surface and immediately smash them into thin patties. Season with salt and pepper.

5. 5

   Cook 1–2 minutes until the edges are crispy, flip, and lay a slice of American cheese on each patty. Cook until melted.

6. 6

   Stack two patties together so the cheese fuses the layers.

7. 7

   Butter the cut sides of the buns and toast until golden.

8. 8

   Spread sauce on the bottom bun, layer pickles, lettuce and tomato, add the double cheese-fused patties and caramelized onions, more sauce if you like, then crown with the top bun.

9. 9

   Enjoy ..

   

Variations to try

• Swap American cheese for pepper jack and add a few pickled jalapeños for a spicy version
• Go true 'animal style' by cooking the onions right into the patty during the last minute of searing
• Make it a single instead of a double by using just one patty per bun for a lighter portion
• Use ground turkey or a plant-based ground substitute, but add a splash of oil to the meat mixture since leaner blends smash and crisp less easily

Storage & make-ahead

Store leftover cooked patties and sauce separately in airtight containers in the fridge for up to 3 days; keep buns, lettuce, and tomato separate so nothing goes soggy. To reheat, warm patties in a hot skillet for a minute or two per side to bring back some crisp, then rebuild the burger fresh. The sauce and caramelized onions both keep well for up to a week and actually taste better the next day, so making those ahead is the best head start for burger night. Freezing isn't recommended once assembled, but you can freeze uncooked seasoned beef balls on a tray, then bag them for up to 2 months.

Frequently asked questions

Why do you season the beef after it hits the pan instead of before?

Salting ground beef too early draws out moisture and can make the patties dense; seasoning right after the smash keeps them tender while still getting good flavor on that crispy crust.

What if I don't have a griddle?

A large heavy cast-iron or stainless steel skillet works just as well — just make sure it's fully preheated over high heat so you get that instant sizzle and sear when the beef hits it.

Can I make the sauce without pickle relish?

You can substitute finely chopped dill or sweet pickles in a pinch, but relish gives the smoothest texture and closest match to the original drive-thru spread.

How do I get the patties thin enough without a special smash tool?

A sturdy metal spatula works fine — press down hard and evenly right when the beef ball hits the hot pan, holding it flat for a few seconds before letting go.