Par-bake the focaccia at 220C/430F for 15 minutes.
Remove from the oven and sprinkle the remaining ⅓ of the cheese on top.
Return to the oven and bake for another 10-12 minutes or until the potatoes and cheese on top have gone golden brown and crispy.
Wait for at least 15-20 minutes before cutting into the focaccia au gratin.
