In a medium saucepan, mix all ingredients with a wire wisk or electric mixer set at low speed until well blended (make sure there are no lumps).
Bring the mixture to a boil over medium heat, stirring constantly. Turn heat to low and continue to cook, stirring constantly, until the mixture thickens. Beat with a wire wisk or electric mixer to ensure that it is smooth.
Transfer the custard to a bowl or individual serving dishes and refridgerate until set. Sprinkle with cinnamon before serving.