Mix flour, salt and oats. Rub in the butter and then knead in the potatoes until a stiff dough is formed. Roll out to about one-eighth-of-an-inch thickness. Cut into three-quarter inch rounds. Put on baking sheets and cook at 325°F, 170°C, gas mark 3 for 20–25 minutes until crisp and brown. Cool on a wire rack. These biscuits are excellent with cheese.