Grate the raw potatoes into a clean cloth placed over a bowl.
Twist the cloth to wring a starchy liquid from the potatoes. Place the grated potatoes in a different bowl and cover with the mashed potatoes to prevent them turning black. When the liquid from the potatoes settles, the starch will drop to the bottom. Carefully pour off the clear liquid from the starch.
Now mix the starch into the potatoes. Add sufficient buttermilk or fresh milk to make a thick batter. Cook on a lightly greased pan over a moderate heat until cooked though and brown on both sides.