Optionally, let eggs, milk, and butter come to room temperature.
Preheat oven to 425F / 220C. Put a heavy 9-inch / 23-centimeter diameter, pan on the middle rack of the oven to heat. Let the pan heat in the oven for at least 15 minutes so it is very hot.
Put eggs, flour, half and half or milk, flour, sugar, salt, nutmeg, and vanilla in a blender and mix for 30 seconds. Alternatively, put the ingredients in a bowl and mix until smooth. The batter should be very thin.
Remove the pan from the oven and add the butter to the pan. The heat from the pan should be enough to completely melt the butter. If not, return the pan to the oven or heat over the stovetop until the butter is melted.
Add the batter to the heated pan with butter, and cook for 25 minutes.
1) It is not necessary to heat up the ingredients but the pancake will puff up better if the ingredients are at room temperature. The half and half or milk can be warmed in the microwave for 20 to 30 seconds. 2) The pan must be heated as described in the recipe. A heavy pan works best since it will retain more heat. The pan should have edges that rise vertically or nearly so, instead of at an angle. 3) If using a blender, it is best to add the eggs first, then flour, then half and half or milk. If you add the flour first it may not blend well, and if you add the flour before the half and half or milk, you do not need to wash and dry the measuring cup between adding ingredients. 4) If topping with powdered sugar, use a fine meshed sieve or sifter for a beautiful snow effect.