Caperberries are like capers but they're crunchier, milder and larger. If you are a caper fan, you'll agree they're also wonderful served in a muffaletta sandwich. They're completely optional in this recipe though, so you can leave them out if you don't like capers or you don't have caperberries. You should be able to find them in the same aisle you'd get olives and capers. You can also buy them in a jar or fresh from a deli.