Crack eggs into a bowl.
Combine the corn starch and eggs, mix well and set aside.
Pour 4 cups milk into a saucepan and add the sugar. Mix well.
Place the pot with the milk and sugar over a medium-heat burner.
Add the egg and cornstarch mixture to the pot and mix well.
Cook over medium heat, stirring constantly. It will take about 8 to 10 minutes for the mixture to start steaming, 10 to 12 minutes to start thickening as you stir, and it will be boiling about 15 to 20 minutes after you started heating. Times can vary depending on pot size/thickness and burner heat level.
Stir constantly until mixture reaches a slow boil.
Remove from heat and cover. Let cool about 20 to 30 minutes.
One cooled some, add the 1/2 cup milk, salt, and vanilla.
Transfer to a jar or container to cool in your fridge - at least 12 hours or overnight, or up to 24 hours.