1) you are going to be in Niseko for the ski/snowboard 2019/2020 season
2) you are willing to spend 10,000 yen per person on this meal
3) you can afford a two-hour lunch
then you might like to check out this place. Known for its delicious and much sought-after SOBA ( customers have been known to queue for an hour or more for their 20 servings of SOBA per day), this restaurant has recently converted to an online reservation only operation and upgraded from a simple Soba type place to a 9-course meal that culminates with a hot or cold Soba with classic or duck soup.
Their soba was absolutely delightful! I got the cold soba with fresh mushrooms, which is one of their specialties. The restaurant follows a traditional design; and you dine cross-legged on a tatami mat. 👍🏼