Preheat oven to 450?. Sift flour, baking soda, baking powder, cinnamon and salt together and set aside. In a large bowl beat the brown sugar, butter and potatoes together until very smooth. Gently stir in thirds of the dry mixture, alternating with the milk. (Stir just tol blend; don't overwork the dough). Roll out the dough (it will be sticky) on a floured surface with a floured rolling pin. Cut with a cutter or into rectangles. Bake for 20 minutes on a lightly greesed pan on a rack placed in the center of the oven.