Preheat oven to 375° F. Mix sweet potatoes, milk, egg, and melted butter and beat well. Sift in the flour and baking powder, then add it to the wet mixture along with the sugar, salt, cinnamon, and raisins.
At this point, you have two options: You can either drop the batter by the spoonful onto greased cookie sheet or you can chill for 1 to 2 hours and then turn onto a floured board, knead lightly, and roll out 1/2-inch thick and cut with a cookie cutter. [Editors' Note: We used the drop method.]
Sprinkle cinnamon sugar on the cookies, then bake for 15 minutes.