Preheat oven to 375°F. Grease a 9x13 baking dish.

Peel, chop, and boil sweet potatoes until tender, then drain and mash.

Stir mashed potatoes with sour cream, brown sugar, melted butter, salt, and pepper until smooth.

Fold in cranberries and half the cheddar. Taste and adjust salt.

Spread mixture into the dish, top with remaining cheddar and breadcrumbs if using.

Bake 20–25 minutes until cheese is melted and topping is lightly browned. Let sit 5 minutes before serving.