There are numerous distinct styles of pepperoni, one of which is Old World pepperoni, the type that cups up when you cook it, allowing the edges to get a bit charred and crisp.

It's typically spicier than standard, flat pepperoni, and when it cups, you get a little pool of chili-infused oil in the center. It brings more flavor and texture to pizza.

The key to Old World pepperoni's cupping magic lies in its natural casing, unlike other types of pepperoni that are stuffed into a synthetic casing made of cellulose or plastic.

Natural casings are made from submucosa, a layer of collagen that is part of animal intestines such as sheep, cow, pig, and goat. They don't need to be removed before eating.

This means that each slice of Old World pepperoni is surrounded by a ring of natural casing. It's the way the pepperoni is stuffed into the casing that gives it a cupped shape.