When Donald Link bakes these cheesy, cayenne-spiked potatoes for himself, he increases the amount of butter and salt because, he says, "They're the two most important ingredients for making really good stuffed or mashed potatoes."
Preheat the oven to 375°. Rub the potatoes with the olive oil and season with salt and black pepper. Bake directly on the oven rack for about 1 hour, or until tender. Let stand until warm. Leave the oven on.
Halve the potatoes lengthwise. Scoop the potato flesh into a bowl, leaving a 1/4-inch-thick shell. Add the scallions, cheddar, sour cream, butter, cayenne and nutmeg and mash until smooth; season with salt and black pepper.
Scoop the filling into the potato skins and bake for about 25 minutes, until heated through and golden on top. Serve the potatoes hot.