1In a medium saucepan, combine the unsweetened cocoa powder, sugar, and salt.
Add 1 cup of the low-fat milk and whisk until the mixture is smooth and the cocoa and sugar are dissolved.
Place the saucepan over medium heat and gradually whisk in the remaining 3 cups of milk.
Heat the mixture, stirring frequently, until it is hot but not boiling.
Remove the saucepan from the heat and stir in the vanilla extract.
Pour the hot chocolate into mugs and serve immediately. Enjoy!