4 tablespoons butter
1 onion, thinly sliced (I'm using yellow)
Kosher salt and freshly ground black pepper
1 1/2 pounds ground meat (I'm using beef)
12 ounces melty cheese, thinly sliced or shredded (I'm using provolone)
4 hoagie rolls or any kind of bread or bun you have, split
For more ingredient substitution ideas, see the article below.