“Toffee is basically sugar and butter,” they write in an email. “Caramel is sugar and cream or milk, with butter occasionally in the mix.” To make toffee crunchy, it is cooked to 300 degrees Fahrenheit, while caramel stays smooth when cooked to about 248 degrees Fahrenheit (but hardens at around 270 degrees).

“To get that chewy, gooey texture of caramel, you have to add a liquid, like milk, cream, or condensed milk,” says Christina McCoy Cohn, co-owner of the Nashville Toffee Company in Tennessee. Because caramel is cooked to a lower temperature, it retains some of the moisture from these liquids, creating a softer texture, says Doug Simons, president of the Enstrom’s candy company.

On a microscopic level, Simons says, you’re creating two types of sugar crystals by cooking the candies differently. In toffee, you get short-grain crystals, which make the candy break easily, whereas caramel’s long-grain crystals enable it to bend.

CHOW’s Nagging Question column appears every Friday.