Because of the high fat content of Kobe beef it should be cooked low and slow.
Whether grilling or cooking in a pan, start on high to sear both sides. Then turn heat down to medium. The cooking time will depend upon the thickness of the steaks and the desired done-ness. And a meat thermometer is a great way of ensuring the perfect result. On average, 3 minutes each side will produce medium rare and 5 minutes each side will produce well done.
As a guide the following temperatures should give you the done-ness you require:
52C - 125F - rare 57C - 135F - medium rare 63C - 145F - medium 71C - 160F - well done
Heat oven to 40C/100F/gas mark 1/4. Place meat in a pan and add 1 - 2 inches of water. Put in oven uncovered. Cooking time will depend upon size of the joint and required done-ness but on average it will take 2 -3 hours for a 2 - 3 kg joint. The end result will be a crunchy, crispy exterior and a juicy interior. Allow to sit for 15-20 minutes, carve and enjoy.
Thermometer temperatures and corresponding done-ness are the same as for the steaks.