Heat frying pan or griddle on medium, and coat with 1 T olive oil or spray with cooking spray. Add onions and cook for 2-3 minutes until browned or even caramelized. Remove onions and set aside in a small bowl.
Heat remaining 1 T of oil (or cooking spray) in pan. Add shaved beef and season with salt and pepper. Use a spatula or two wooden spoons to gently pull shaved beef apart and cook until no longer pink. Mix in onions.
Slice hoagie rolls lengthwise without completely slicing apart. Spread butter on the inside of each half.
Divide meat into sections in your pan, depending on how many rolls you have. Place 1-2 slices of cheese on top of each section of meat. Then, lay the open side of the roll face down on the cheese & meat for 1-2 minutes, or until butter and cheese have melted. Use one or two spatulas to gently flip over meat with roll onto a plate. Serve cheesesteaks with your side of choice.
To plate...serve cheesesteaks with your side of choice.
Shaved beef is the best meat for these cheesesteaks.
Assemble your cheesesteak upside down in the pan. Use a spatula or two to flip assembled cheesesteaks over and onto your plate.