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Double Smashburgers with Caramelized Onions + Burger Sauce

These double smashburgers are loaded with crispy-edged beef patties, melted cheese, caramelized onions, and a tangy homemade burger sauce on toasted buns. It’s the kind of rich, satisfying comfort food that turns an ordinary Monday night into the perfect excuse to fire up the griddle, pour a drink, and enjoy a good cigar after dinner.
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Prep Time 15 minutes
Cook Time 29 minutes
Course Main Course
Cuisine American
Servings 4 people
Calories 1050 kcal

Equipment

  • 1 Large Skillet, Cast-Iron, Flat Top Griddle or Blackstone
  • 1 Medium Skillet for Carmelizing Onions
  • 1 Sturdy Metal Spatula or Burger Press
  • 1 Mixing Bowl for Burger Sauce
  • 1 Cutting Board
  • 1 Chef's Knife
  • Measuring Cups and Spoons
  • Small Whisk

Ingredients
  

Burgers

  • 2 lbs 80/20 Ground Beef
  • 8 slices American Cheese
  • 4 Brioche or Potato Buns
  • 1 large Yellow Onion thinly sliced
  • 2 tbsp Butter
  • 1 tbsp Olive or Avacado Oil
  • Salt
  • Pepper

Burger Sauce

  • 1/2 cup Mayonnaise
  • 2 tbsp Ketcup
  • 1 tbsp Yellow Mustard
  • 1 tbsp Finely Diced Pickles or Sweet Relish
  • 1 tsp Pickle Juice
  • 1/2 tsp Smoked Paprika
  • 1/4 tsp Garlic Powder
  • Black Pepper

For Serving

  • Dill Pickle Chips
  • Shredded Lettuce
  • Extra Mayo & Mustard
  • Crispy Bacon
  • Fries, Chips, or Onion Rings Side

Instructions
 

Make the Burger Sauce

  • Start with the sauce so the flavors have a little time to come together while you cook.
    In a small bowl, stir together the mayonnaise, ketchup, mustard, diced pickles or relish, pickle juice, smoked paprika, garlic powder, and black pepper. Taste it and adjust if needed. If you want it tangier, add a touch more mustard or pickle juice. If you want it sweeter, use sweet relish instead of dill pickles. Set it in the fridge until you are ready to build the burgers.
    This sauce is not fancy, and it does not need to be. It is creamy, tangy, slightly smoky, and exactly the kind of thing a smashburger wants.

Carmelize the Onions

  • Heat a skillet or griddle over medium heat and add the butter. Once it melts, add the sliced onion with a pinch of salt. Cook slowly, stirring every few minutes, until the onions soften and take on a deep golden-brown color. This usually takes around 20 to 25 minutes if you are doing it right. Do not rush them. If the pan gets too dry, add a tiny splash of water to loosen the browned bits and keep the onions moving.
    You are not trying to burn them. You want them soft, jammy, and sweet, the kind of onions that melt into the burger instead of sitting on top of it like an obligation.
    Once they are done, move them to a bowl and keep them warm.

Prep the Beef

  • Divide the ground beef into eight equal portions, about four ounces each. Gently roll them into loose balls. Do not pack them tightly. The whole point is to keep the beef tender while giving it enough surface area to form that glorious crust.
    Season the outside lightly with salt and pepper just before cooking. If you salt too early, it can start to change the texture of the meat.

Toast the Buns

  • A burger deserves a toasted bun. It is one of those small details that makes the whole thing better.
    Set your griddle or skillet over medium heat, brush the cut sides of the buns lightly with butter or mayo, and toast until golden brown. Set them aside.

Smash and Cook the Burgers

  • Now for the fun part.
    Heat a cast-iron skillet, flat-top griddle, or Blackstone until it is very hot. You want real heat here. Add a small drizzle of oil if needed, then place two or three beef balls on the surface, depending on how much room you have.
    Using a sturdy spatula, burger press, or another heavy flat object, smash each ball down hard into a thin patty. Do it quickly, once, and do not fuss with it after that. The goal is a thin burger with lots of contact against the hot surface.
    Season with salt and pepper and let the patties cook undisturbed for about 2 minutes, or until the edges are deeply browned and crisp. Scrape them up with a strong metal spatula, flip them, and immediately top four of the patties with cheese. Cook another 30 to 60 seconds.
    Stack one plain patty on top of one cheese-topped patty to create a double burger. Repeat until you have four doubles.
    If you are adding bacon, this is your moment to pile it on. If you are not, no one will accuse you of lacking vision.

Build Your Burgers

  • Spread burger sauce on both sides of the toasted buns. Add a layer of lettuce if you want some crunch, then place the double cheeseburger on the bottom bun. Top with caramelized onions and dill pickle chips. Add tomato if that is your thing, though I personally think a smashburger is happiest without it. Crown it with the top bun and try not to lose half the burger down your wrist on the first bite.
    Serve with fries, kettle chips, or onion rings and plenty of napkins.

Notes

  • Use 80/20 ground beef for the best crust and flavor.
  • Smash the burgers immediately after they hit the hot cooking surface, and only smash once.
  • A cast-iron skillet or flat-top griddle works best for developing those crispy burger edges.
  • Toasting the buns helps keep them from getting soggy once the sauce and burger juices hit.
  • American cheese gives the most classic smashburger melt, but cheddar or pepper jack also work well.
  • Burger sauce can be made ahead and refrigerated until ready to use.
  • Nutrition estimates are for the burger only and do not include fries, chips, or optional drink pairings.
Keyword Burgers