How to Make It
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.