Kofuki Imo gets its name (Powdered Potatoes) by the cooking method. As the boiled potatoes are gently stirred in the soy sugar coating, they become slightly mashed. This creates a powdered look on the surface of the potatoes. Kofuki Imo is an easy to put together side dish. I have also made them a few times for breakfast. I really enjoyed the combination of soy sauce and butter.
The potato is a more recent addition to Japanese cuisine. It was first introduced by the Dutch in the 17th century and the growing their own crops began in the 1800s. The potato now has many uses, including in this dish. Other popular dishes using Jaga-imo (potato in Japanese) are Nikujaga (Beef and Potato Stew) and Japanese curry.
More information on vegetables in Japanese cooking