Makes 6 servings
1. Combine 1 cup of the milk, ½ cup of the sugar, and the salt in a medium saucepan and bring to a boil over medium heat, stirring gently with a wooden spoon.
2. Meanwhile, in a medium bowl, combine the cornstarch with the remaining ½ cup sugar. Stirring with a whisk, add the remaining cup of milk. Add the egg yolks, stirring with the whisk until the mixture is completely smooth.
3. Slowly add about one third of the hot milk to the bowl, stirring constantly with the whisk. This is called tempering. Return the tempered egg mixture to the remaining hot milk in the saucepan. Continue cooking, stirring constantly with the whisk, until the pudding comes to a boil. Remove from the heat and stir in the butter and vanilla.
4. Pour into serving dishes and cover, pressing plastic wrap directly on the surface of the pudding to prevent a skin from forming. Refrigerate until fully chilled.