Swiss Rocher is chocolate that has crunchy bits of nuts in it. Sometimes there’s praline, sometimes the nuts are caramelised, sometimes not.
Whatever, it makes for a (if you like nuts, that is) really moreish, delicious chocolate. Rocher means rock in French, so traditionally these are ball shaped. And often if you go into a chocolate shop, you’ll see them, nut-studded golf ball-sized chocolate rounds. I really like them, because they’re big enough to be indulgent, and once you bite in you just have to keep going.