Mix the sake, soy sauce, mirin, honey and ginger in a bowl. Add the diced turkey and leave to marinate for at least 15 minutes. Meanwhile, bring the diced potato to boil in lightly salted water. Simmer for about 15 minutes until just cooked, then drain and keep warm. Fry the turkey to brown in a pan, reserving half the marinade for later. Add the vegetables, tossing well. Pour in the reserved marinade, simmering for a few more minutes. Take off the heat and tip into your pie dish. Mix the milk and sesame oil into the pan of potato and mash well. Spoon the mash atop your pie filling, and scatter over the sesame seeds. Bake at 190 degrees C for about 25 minutes until the potato looks nice and crispy.