Preheat oven to 350 degrees F. Mash sweet potatoes; stir in 1-1/4 cups sugar and butter until smooth. Add eggs; blend well and set aside. In a separate bowl, mix together flour, baking powder, salt, nutmeg and one teaspoon cinnamon. Add to sweet potato mixture, alternating with milk; stir just until moistened. Fold in raisins and walnuts. Fill 24 paper-lined muffin cups 3/4 full. Mix remaining sugar and cinnamon; sprinkle over top. Bake at 350 degrees F. for 25 to 30 minutes, until a toothpick inserted in center tests done. Serve warm.