Oil a small 3-4 cup souffle mold, or individual custard dishes, then line with cling film.
Mix the cornstarch, ¼ cup sugar, egg yolks, orange zest, lemon and water to make a slurry.
Heat the nannyberry butter and the half and half, whisking, until hot and steaming, but not boiling.
Stir in the cornstarch-egg slurry and whisk constantly, keeping the heat at medium, until the mixture thickens, then turn the heat down to as low as possible and continue whisking for a few minutes more, or until you can tell the cornstarch is completely activated.
Take the pan off the heat and whisk in the butter, then transfer the pudding to the prepared mold(s) and refrigerate overnight, or until the pudding is set and able to be unmolded.
Nannyberry Mousse
Whip 1 cup of cream to soft peaks and gently fold into the pudding when it’s completely cooled to room temperature, then refrigerate. Before serving, spoon the mousse into custard cups. Good garnishes could be fruit coulis, orange custard sauce, persimmons, and or toasted nuts, especially black walnuts.
Notes
The mousse can be made days ahead of time, packed into a pastry bag as pictured, and piped into whatever vessel you like just before serving. It can also be used as the filling for a crepe cake, or another dessert you could serve chilled.A splash of Gran Marnier or Tuaca is nice to add while the pudding is cooking, if you have some.