Preheat oven to 375°. In a small bowl, combine flour, sugar and cinnamon. In another bowl, whisk egg, sweet potatoes and oil. Stir into dry ingredients just until moistened.
Fill greased muffin cups two-thirds full. Bake 15-18 minutes or until a toothpick inserted in muffin comes out clean. Cool 5 minutes before removing from pans to wire racks.
In a small bowl, combine glaze ingredients; drizzle over warm muffins. Freeze option: Freeze unglazed cooled muffins in resealable plastic freezer bags. To use, thaw at room temperature or, if desired, microwave each muffin on high until heated through, 20-30 seconds. Glaze.
As a substitute for each cup of self-rising flour, place 1-1/2 teaspoons baking powder and 1/2 teaspoon salt in a measuring cup. Add all-purpose flour to measure 1 cup.