Knead the minced beef with the burger seasoning, ketjap manis, eggs, breadcrumbs, milk. Season with salt and pepper. Shape with wet hands into 4 equal burgers.
Heat the butter in a large frying pan. Fry the burgers over a high heat on both sides until brown. Turn down the heat. Cook for another 10 minutes with the lid on the pan. Turn them halfway. Prefer the burgers rare? Simply reduce the cooking time.
Meanwhile, slice the tomato. Cut the avocados all the way around the stone. Twist the two halves apart. Remove the stone, scoop the flesh out of the skin and cut into thin slices.
Fill the rolls with the lettuce, tomato, burger, cheddar and avocado.
