Here’s a bit of nostalgia. Chocolate with popping candy (pop rocks) in them were pretty popular back in the 90s. A couple of supermarkets and candy stores in The Netherlands still sell these. (In Dutch we call this ‘knetterchocolade’.)
Pop rocks, popping candy or ‘sparkling candy’ is a type of confectionery that produces a fizzy or crackling sensation in your mouth when you eat it. Popping candy contains carbon dioxide. When it comes in contact with moisture, such as saliva in your mouth, it releases gas bubbles, creating the popping or crackling sensation. It makes for a fun eating experience!