In a medium saucepan, heat the milk and cinnamon stick over medium heat until it begins to simmer.

In a separate bowl, whisk together the sugar, egg yolks, and cornstarch until smooth.

Remove the cinnamon stick from the milk and gradually pour the egg mixture into the saucepan while continuously whisking.

Cook the mixture over medium heat for about 10-15 minutes or until it thickens, stirring occasionally.

Remove the mixture from the heat and stir in the vanilla extract.

Pour the mixture into a serving dish and let it cool to room temperature.

Once cooled, sprinkle ground cinnamon over the top and refrigerate until ready to serve.