Bake sweet potatoes at 400°F for about 45 minutes until tender.
Whisk yolks, sugar, vanilla, and cornstarch. Slowly add cream until smooth.
Cook mixture in a small pot over medium heat, stirring until thickened. Chill if serving cold.
Cut open tops of baked potatoes, scoop a little flesh, and fill with custard.
Sprinkle sugar on top, torch until golden and crisp.
