read here), two readers, Rodzilla and Chris, both answered my query! (Big thanks, readers!) Apparently the flavor is Milk Coffee, which I never would have guessed. Years ago my friend Matt purchased a case of the American release of Coffee Kit Kats (and unfortunately I consumed about half of that case) and they tasted so distinctively of coffee. I guess the Milk element of these Milk Coffee bars is the primary flavor with a more subtle Coffee undertone. As I said, they're good and I consumed them in seconds, but it's not an obvious connection to the flavor they're striving for. The Royal Milk Tea Kit Kats (read review here) were also heavy on the Milk flavor, but the underlying Tea flavor was a bit more distinctive than the Coffee.