Mix the potatoes, butter and milk and mix into the mixture of the flour, baking soda and salt.Knead lightly on a floured surface for 5 minutes, form into the desired shape and place on a greased baking pan or cast iron skillet.Bake in a preheated 400F/200C oven until golden brown, about 30-40 minutes.Let cool for 20 minutes before slicing and enjoying!