Boil potatoes in water until soft (about 25 minutes).
Meanwhile, in a medium-hot nonstick skillet, sauté corn kernels until soft, about 5 minutes.
In a food processor, blend corn to a paste-like consistency.
In a large mixing bowl, mash potatoes using a wire whip. Add corn, hot milk, sour cream, and nutmeg (optional). Whisk until potatoes are fluffy. Serve immediately.