Preheat the oven to 375°F (190°C).
Wash and scrub the sweet potatoes. Pierce them all over with a fork.
Place the sweet potatoes on a baking sheet and bake for 1 hour, or until tender.
Remove from the oven and let them cool slightly.
Cut the sweet potatoes in half and scoop out the flesh into a large bowl.
Add the butter, milk, brown sugar, cinnamon, nutmeg, salt, and pepper to the bowl.
Using a potato masher or electric mixer, mix until smooth and creamy.
Transfer the mashed sweet potatoes back to the baking dish.
Bake for an additional 15 minutes, or until heated through.
Serve hot and enjoy!