Start by slicing the hoagie rolls lengthwise, spread butter on the insides, and toast them in a skillet over medium heat for 2-3 minutes until golden brown.

In the same skillet, add ground beef and chopped onions, season with salt and pepper. Cook for 6-8 minutes, stirring frequently until browned.

Lower the heat and lay American cheese over the beef mixture. Chop and mix until cheese melts thoroughly, about 2-3 minutes.

Spread mayo and ketchup inside the toasted rolls, then fill generously with the beef and cheese mixture, topped with lettuce and tomato.

Serve hot and enjoy your delicious chopped cheese sandwich!