Irish Potato Biscuits

Preheat oven to 400 degrees F. Boil and mash the potatoes, making sure they are free of lumps. Add the milk, butter, and salt. Add just enough flour to make a soft dough, then lay it on a floured board and roll out quickly and lightly to a half-inch sheet. Cut into rounds; bake about 10 minutes, or until just crisp on the outside. Butter and eat before they fall.