Another recipe that I found online (allrecipes.com) and tweaked a little...
Mix together and set aside:
2 1/2 Cups flour (if using self-raising flour omit baking powder and salt)
1 1/2 tsp baking powder
1/4 tsp salt
1/2 tsp baking soda
In a seperate bowl cream together 1/2 Cup butter/margarine/applesauce and 1/4 Cup white sugar, 2 Tablespoons brown sugar.
Add 1 1/2 tsp lemon zest/lemon juice
1/4 tsp nutmeg
1/4 cup honey
1 tsp vanilla
Mix in 1 Cup grated (raw) sweet potatoe.
Stir in to flour mixture.
Drop 2 inces apart on ungreased cookie tray. Bake on 350 for 7 minutes. Remove from oven and leave on tray for 5 minutes before removing to cool on wire rack.
Spread/drizzle with mixture of powdered sugar and fresh lemon juice. Add water to desired consistency.