1. Combine 3 cups of the milk with the sugar and salt in a heavy-bottomed medium saucepan and set it over medium-low heat. If you are using the vanilla bean, scrape out the seeds, put them in the milk, and add the whole bean heat until just steaming, stirring frequently.

2. In a small bowl or measuring cup, combine the cornstarch with the remaining 1 cup of milk. Stir well until the mixture is fairly lump free. Take the vanilla bean out of the pot and rinse it off. (Don't discard it- shove it into your homemade Vanilla Extract). Raise the heat to medium-high. Add the cornstarch mixture and cook, stirring constantly with a wooden spoon, until the mixture just starts to bubble. Reduce the heat to low and stir continuously until the mixture thickens to somewhat look like pudding and coats the back of a spoon, 5-7 minutes. Add vanilla extract, if using. If the pudding us a bit watery, it's okay. It will thicken further as it chills.

3. Pour the pudding into individual dishes and chill for at least 3 hours before serving. If you have an aversion to pudding skin, press plastic wrap against the surface.