
Dark chocolate mint is one of my all-time favorite combinations, and is to me the culmination of man's historical fascination with mint. Dark chocolate bars and squares, with mint filling or mint infused with the chocolate, are produced by many different manufacturers.
Some History

Originally native to the Mediterranian and western Asia, mint has been known and used for medicinal purposes, and for its wonderful breath freshening qualities, for thousands of years. It is referenced in the Bible, and in Greek mythology. Mint flavorings are made from highly concentrated mint oil, usually made from peppermint, spearment, or from the many various other forms.
When the Spanish first brought dark chocolate to Europe, they experimented with many addtional flavorings for sweatening the chocolate. Mint was one of these sweateners. In the mid-19th century, when solid dark chocolates were first being manufactured, mint flavored chocolates were included.
But it wasn't until the 20th century that dark chocolate with mint became really popular. In the US, it may have been the Junior Mint, introduced in 1949, that popularized the dark chocolate and mint combination. I was introduced to the After Eight when I lived in England in the early 1970s. If I had to live off of only one dark chocolate for the rest of my life, it would be the After Eight.
There are now two basic types of dark chocolate with mint products: dark chocolate with a mint filling, and dark chocolate with the mint flavoring infused within the chocolate itself.

Dark Chocolates With Mint Filling

Dark Chocolate With Infused Mint