Preheat oven to 375 degrees.
Combine cooked, mashed sweet potatoes, brown sugar, half and half, butter, salt, orange peel, spices and pepper. Mix well.
Spread the sweet potato mixture in a greased pan about 7x12 up to 9x13.
Combine topping ingredients: 1/3 cup brown sugar, chopped pecans, melted butter and cinnamon in a small bowl.
Sprinkle over sweet potato mixture.
Bake at 375º for 30 minutes or until thoroughly heated.