The smashburger is the original burger. It’s simple, classic, and built for flavor.
Start with a potato bun: buttered, toasted, and smeared with burger sauce (think of it as a mix of standard condiments, but with a little extra flavor). For a guaranteed great bun, get Martin's sandwich potato rolls. Add a layer of shredded iceberg lettuce on the bottom bun to prevent the burger juices from turning the bun into a soggy mess.
Not all ground beef is created equal, so take the time to find a good butcher. Any 80/20 ground beef will work, but if you want to really make an amazing burger, use a trimmed chuck roast and add in pork fatback. (This probably means grinding your own meat, which isn't hard, but requires special equipment.)
For each burger, take two 2.5oz balls of ground beef and smash them onto a flat top griddle, then salted and peppered. Really smash them thin, to the point that you can see holes in the patty — this is called "lace" sometimes, and it creates extra surface area for delicious crispiness. Almost all of the cooking happens on this one side to capitalize on the Maillard magic.
Once the patties are nearly cooked through, flip them and salt and pepper the other side. The bottom patty gets a pile of thinly sliced red onions (use a mandolin to make these really thin), then both patties get a slice of American cheese.
Putting the red onions on top of the patty and under the cheese means they soak up some of the juices from the burger, which adds a ton of extra flavor and starts cooking them a bit, leading to all the good things of fresh onions and all the good things from sauteed onions.
Why American? Because nothing melts like American cheese, and with a smashburger it's important to use the cheese as a binding agent to prevent the patties from falling apart. A good smashburger is held together with nothing but love and American cheese.
The cheese will melt quickly, at which point the patty without onions is stacked on top of the other, then both are placed on top of the bottom bun.
The top bun gets a smear of burger sauce. Add pickles (for best results, use Best Maid hamburger slices), put the bun on top, and take a bite of the best damn burger around.