Then come the peppers. An Italian beef sandwich with “sweet” is topped with peppers and a beef “hot” is layered with giardiniera. Sweet peppers are typically green (but also red) bell peppers cut into fat, long chunks that you can lay across the length of the sandwich, tossed with olive oil, fresh garlic, salt, and pepper. The "hot" in an Italian beef comes from giardiniera, a pickled relish of spicy peppers and vegetables. Most bigger beef stands make their own giardiniera, a process that many say is more complicated than actually making the beef.
And finally comes the bread. “The bread used for beef sandwiches is of a type that old Italian bakeries in Chicago called 'French bread' and is distinguished from basic Italian bread in having a longer, narrower shape, thinner crust, and a softer, hole-less crumb,” writes Buccini. “Small Italian bakeries and large-scale Italian bakeries of Chicagoland (Turano, Gonnella, D’Amatos) are favored sources for this bread.”
Devivo says the key to a good Italian beef sandwich is the seasoning, the way you slice the beef during prep (you want it really thin “but not shredded”), and the peppers. “Anyone can take a piece of raw meat and cook it,” he says. “The spices that you use differentiate your Italian beef from another place. It all comes down to the customer’s preference.”