Portion your mince into 4 x 125g balls and roll them until smooth. Slice your onion finely and portion into 4 x 25g. Place one portion of onion and one beef ball on a square of baking paper. Cover with another square of baking paper and using the palm and heel of your hand squish the beef into the onion and into a thin patty. Depending on the size of your burger bun, is how far to squash your patty. I always smash my burger so that it is about 1-2 cm bigger than the bun, as it shrinks when cooked.
In a frypan, on the bbq or flat top, heat to medium heat. Butter the halved burger buns and toast until nice and golden brown. Turn up heat to med-high.
Add a generous amount of burger sauce to top and bottom buns, and add 3 pickles to each top bun.
Peel away the baking paper from one side of the burger, and place the burger onto the hot cooking surface. Peel away other side of baking paper, and season the burger surface with salt and pepper. Cook burgers for approximately 3 minutes per side, or until nice and caramelised. Flip the burgers and add a slice of American cheese to the top. Cook for about 3 minutes or until nicely caramelised again.
Add the burger to the bottom bun, top with the top bun, and you're ready to eat. I suggest serving with shoestring fries and the leftover burger sauce for dipping.