In a heavy saucepan, combine milk, lightly beaten eggs and powdered sugar, and mix well using a wire whisk.
Slowly bring to a simmer, over low heat, for 5 minutes, stirring frequently with the whisk.
Remove from heat.
Add vanilla extract and mix well.
Refrigerate until cold.
To serve, heat eggnog in the microwave, garnish with nutmeg, and serve warm as a morning drink.
For a cold variation, pour mixture into blender container and add one cup of crushed ice.
Blend until frothy.