Heat the milk: In a pot, mix together the milk, orange zest, and half of the sugar. Heat over medium heat until it’s just about to boil, stirring constantly to ensure it doesn’t scorch.
Prepare the orange mixture: In a separate bowl, combine the corn starch, the remaining sugar, egg yolks, and fresh orange juice. Beat until everything is well integrated.
Temper the mixture: Gradually pour half of the hot milk into your orange mixture, stirring continuously to prevent any lumps from forming.
Cook until thickened: Pour the entire mixture back into the pot with the remaining milk. Cook over low heat while continuously stirring until the custard thickens (this should take about 4 minutes).
Cool it down: Transfer the custard to a container and cover it with plastic wrap, ensuring it touches the surface to prevent a skin from forming. Place it in the refrigerator for at least one hour to chill.
Ready to serve: Once cooled, give the custard a light whisk before serving. Enjoy it on its own, or use it as a luscious filling in desserts!