Preheat oven to 375 degrees. Place potatoes in saucepan, cover with water and add salt. Boil until cooked. Cut a thin slice off of the potato so it can stand without rolling. ON the top, cut a deep V, Roll potatoes in oil, then sesame seeds, and place them in an ovenproof baking dish. Mix together remaining ingredients and marinate for 5 minutes. put radish slices into V of potato and pour sauce over top. place in oven for 10 minutes until warm.