These cookies derive their umami flavor from furikake, which is a Japanese seasoning, often used on rice.
I've paired them with sesame seed cookies made in the same manner.
These were designed to be both pretty and for you to experience the umami taste first. I'd describe the experience as a salty/savory as the furikake first hits your tongue, then sweet from the cookie, with a finish of black sesame/savory taste. The sesame seed cookies are less flavorful as they don't have the umami element, but are made for a visual complement as well as for those who are not brave enough to try a salty/sweet cookie. Personally I love salty and sweet and put syrup on bacon, so this cookie is right up my alley.
If you are not interested in all the crazy mixing and waiting, but still want to experience the umami cookie there is an alternative to this recipe. You can go buy a roll of Pillsbury sugar cookie dough in a tube and roll that into furikake that you find in a Japanese market. It won't have the same richness as my cookie dough base has cream cheese in it, but it will give you that salty/savory/sweet contrast.