Wash, pierce, and roast Korean yams in 400 degree oven for 35 minutes, or until a fork can easily be slipped in with just slight resistance.
Remove from oven and slice along the length, about ¾ of the way to the bottom.
Mix 2 parts soy sauce, 1 part mirin, 1 part sesame oil, and add some rice vinegar to lighten it up.
Pour the mixture on top of yams, making sure to get in the cracks.
Roast for another 10 minutes, until glaze has infused.
Highly recommend eating with fingers, dragging the pieces through the residual sauce.
