During December 2011, I ordered Rokkatei Butter Sandwich (マルセイバターサンド) from Hokkaido as a new year present for a friend's family, as well as ordering another box for myself. To me, I classify this sweet as a biscuit/cookie because I don't really see another way to classify it. =_="
I've only tasted Aso's Butter Sandwich (Aso is in Kumamota prefecture, Kyushu Island) before, but not the ones from Hokkaido. To my surprises, the Hokkaido's ones are much more creamy and stronger in favor.
A butter sandwich consists of butter/cream cheese filling with raisins, in between of two butter cookies. I think the cream with raisins part to be a bit too sweet. I don't mind the tiny scent of rum, however, I find it too hard to eat without any drink to drown the sweetness. The biscuit didn't help either, as I think they are made from brown sugar. I forgot to take the picture of the butter sandwich before my friend finished the whole 20-pieces box, so the picture of it is founded online. [credit: http://item.shopping.c.yimg.jp/i/j/946kitchen_m-2]
My Japanese friend seems to have enjoyed the Hokkaido's butter sandwich more than the Aso's ones, but somehow, I prefer the weaker taste one from Aso. I found it easier to eat, as I could only eat half of the Hokkaido's butter sandwich before having to put it down to get a glass of milk to lessen the overly sweetness of the biscuit.
Overall, I find this Rokkatei Butter Sandwich not to be overly exciting, or enchanted in anyway. However, Japanese people seems to like it, as it is a very well-known snacks and can be found outside of Hokkaido. I was super surprised when I was a small box of this butter sandwich in Daimaru Osaka-eki. It was a bit of a bummer because the friend's family whom I ordered it for lived in the Kansai area, and I wanted to find something that they can't normally find in the Kansai area.
Oh yeah.. This darling costed quite a penny in my opinion.. 20 pieces for ￥2,300.
You can find out more information on Rokkatei's Butter Sandwich from: https://www.rokkatei-eshop.com/eshop/contents/top/ (sorry, only in Japanese)