The Hakata Torimon is a sweet that was created by Meigetsudo company in 1993. It quickly became very popular to the point where it became a must-get souvenir for people traveling to Fukuoka. Locals also consume it in abundance.
It's what Japanese people call a "manju", or steam bun, but the filling is something of a mix of traditional Japanese and western ingredients. Whereas the traditional manju is filled with sweet azuki bean paste only, the Hakata Torimon has a filling of white azuki beans mixed with butter, eggs, condensed milk and cream which adds a richness that regular manjus don't have. The result is a smooth and unctuous manju that melts on your tongue when you eat it.
So make sure to get it as a souvenir when you visit Fukuoka! You can buy it at the Meigetsu souvenir shop inside the Hakata Station and at many other locations in Fukuoka. For a souvenir box of twelve manju, it costs 1,480 yen. This is really on the cheap side of Japanese souvenir sweets.
The Hakata Torimon is the number one seller but there are also other interesting items such as this manju made with high-quality green tea and dark azuki paste!