How to Make It
Put the potatoes in a large saucepan and cover with water. Add a large pinch of salt and bring to a boil. Simmer over moderate heat until tender, about 20 minutes. Drain the potatoes and return them to the saucepan. Cook for 1 minute over high heat, shaking the pan frequently to dry out the potatoes.
Pass the potatoes through a ricer into a large bowl. Stir in the egg, butter, dry milk, cheese, flour and nutmeg; season with salt. Using floured hands, roll the potato mixture into 1-inch balls; you should have about 60.
Preheat the oven to 350°. In a large nonstick skillet, heat 1/2 inch of vegetable oil until shimmering. Working in batches of about 12, fry the potato balls over moderately high heat until they are browned on 3 sides, 2 to 3 minutes per side. Drain on paper towels, season lightly with salt and transfer the potato balls to a large rimmed baking sheet. Repeat with the remaining balls.
When all of the puffs are fried, reheat them in the oven for about 10 minutes. Serve at once.