Preheat the oven to 375°F (190°C).

Place the diced sweet potatoes in a medium saucepan and cover with water. Boil for about 15 minutes or until fork-tender.

Drain the sweet potatoes well, return them to the saucepan, and mash until smooth.

Stir in milk, butter, garlic powder, salt, and pepper until fully combined.

Spoon half of the sweet potato mixture into a baking dish and sprinkle with half of the shredded cheese.

Top with the remaining sweet potato mixture and sprinkle the remaining cheese over the top.

Bake in the preheated oven for 25–30 minutes, or until the cheese is melted and bubbly.

Let the dish cool for a few minutes before serving to allow the flavors to meld.