Start by mixing your dressing. You can also make a Thousand Island dressing instead if you prefer.
Weigh out the meat into 80-gram patties and roll them into balls.
Finely chop your onion.
Turn up your pan to the highest possible heat. If you have a plancha, a griddle, or a grill plate, it is preferable - as it is easier to remove the "smash iron" since there isn't a rim like on the pan.
When it's hot, add oil. Give it about 30 seconds to heat up.
Add the meatballs and flatten them with a burger press. If you don't have one, you can use the bottom of a coffee cup or even a pot. The most important thing is that the meat is flattened to about 2-3 mm thickness.
Remove the press and season the meat with salt and pepper.
Flip the meat after about 50 seconds.
Place two slices of cheese on top of the patties while they are still in the pan.
Remove the patty after 50 seconds and place it on a cutting board while it rests and the rest of the cheese melts.
If you have cooked multiple patties at once, just stack them on top of each other while they rest - either 2 or 3, it's up to you.
Slice the buns in half and toast the bread on the inside, either on a toaster or in the pan.