Meanwhile, in a small pot off the heat, whisk together the sugar, corn starch and flour. Add the egg and mix well. Add the milk and half of the cream (1/4 cup/60 ml). Add the orange zest. Bring to a boil over medium heat, stirring constantly and making sure to scrape the bottom and sides of the pan, until the mixture thickens. Remove from the heat. Add the passito. Remove the zest. Pour into a bowl and cover with plastic wrap directly on the pastry cream. Let cool and refrigerate for 1 hour 30 minutes or until the cream is completely chilled.
