Float

Pour milk into a large pot and whisk in 1/3 cup granulated sugar. Cook over medium heat until a thin film forms on the top (do not boil).
Whisk together the remaining sugar and the egg yolks until very well-blended.
When the film has formed on the milk, remove it from the heat and pour 1 cup it into the bowl with the egg yolk mixture. Whisk to combine, then add another cup of milk and mix it in. Now that the eggs are tempered, pour that mixture into the pot of milk and whisk until fully combined.
Return the pot to the heat and cook the mixture over medium-low heat, stirring frequently, until it coats the back of a wooden spoon. 

About 20-25 minutes. 

Remove the pot from the heat and stir in the vanilla.

Let the custard cool in the pot for a few minutes, stirring occasionally, then pour it into a two quart jar and chill before serving.