Cut sweet potatoes into thick slices and arrange them in a greased serving oven pan. Season with salt and pepper. Combine sugar with cornstarch, orange juice and salt in a medium size pan. Bring to a boil and cook until light syrup is obtained. Add orange peel, sherry or pisco. Bring to a boil to evaporate alcohol. Add chopped pecans and combine.
Pour over sweet potato slices and arrange between slices peach wedges (optional).
Bake in preheated oven at 350ºF (180ºC) for 25 minutes.