Preheat oven to 375°. Arrange potatoes on a baking sheet lined with parchment. Bake until tender, 1 hour 10 minutes to 1 hour 20 minutes. Remove from oven; let stand until cool enough to handle.
Cut each potato lengthwise. Scoop flesh into the bowl of an electric mixer fitted with a paddle attachment; discard skins. Add 2 tablespoons butter and the cream; mix on medium speed until smooth. Mix in applesauce and ginger; season with salt and pepper.
Transfer potato mixture to an ovenproof dish. Bake until heated through, about 10 minutes.
Meanwhile, toss apples with sugar in a bowl. Melt remaining 2 tablespoons butter in a large skillet over medium heat. Add apple mixture; cook, stirring occasionally, until apples are golden and caramelized, about 10 minutes.
Remove potato mixture from oven; top with caramelized apples, and serve.