That's a very good question flirty! It's very hard to describe isn't it? No particular name-able flavour? Perhaps vanilla would be the nearest description, although it isn't really that either.
What's this brawburd - an actual mint-flavoured Fry's Chocolate Cream, as well as the original version? I'll definitely have to give that one a go. But doesn't that at least tell us that the original version is, indeed, NOT mint? Perhaps, as molly says, it's a secret and we will never know, but we can have plenty of fun trying to find out! (Oooh, I can feel another inch going on the hips now!)