Place the potatoes on a foil-lined baking sheet and bake until tender, 45 minutes to 1 hour, depending upon their size. Remove from the oven and let sit until cool enough to handle. Peel the potatoes while still warm and cut each into several pieces.

Butter a small baking dish and arrange the potatoes in a single layer. Sprinkle with sugar and dot with butter. Return to oven and bake until the sugar melts and the potatoes are glazed, about 15 minutes. Keep warm until ready to serve.