Mix all ingredients together (except beef) until sugar is dissolved. Place beef in shallow and narrow glass or plastic container. Cover with marinade. The liquid should come at least ½ up the sides of the tenderloin medallions. Marinade covered in refrigerator for a minimum of 4 hours and no longer than 12 hours. Turn over every two to three hours.
Clean and oil hot grill. Remove steaks from marinade, pat dry and lightly oil. Boil remaining marinade in pot until it has reduced to the consistency of maple syrup. (Warning: do not use marinade unless boiled for at least 5 mins because it may contain harmful bacteria if used raw. Boiling insures no bacteria can survive.) Grill steaks and glaze with reduced marinade when ready to serve. Serve steaks with wasabi mashed potatoes. For this you may use leftover seasoned mashed potatoes. Just mix 1 teaspoon of wasabi paste (follow package directions) with every 2 cups of prepared mashed potatoes. Stir fried vegetables and bok choy are great accompaniments for this dish.