2 1/2 tablespoons cornstarch
1/4 cup light brown sugar
Zest and juice of 1 large orange
1 egg yolk, lightly beaten
1 teaspoon vanilla extract
Pinch of salt
2 ounces dark or bittersweet chocolate, shaved using vegetable peeler or wand-style grater
In a large saucepan over medium heat, whisk together the milk and cornstarch until dissolved. Add the brown sugar and continue to whisk while bringing the mixture to a gentle simmer. Cook, whisking constantly, until the milk thickens to a thick pudding, about 2 minutes.
Whisk in the orange zest and juice, then remove the pan from the heat.
Place the egg yolk in a small bowl. One at a time, while whisking, add a few tablespoons of the hot pudding to the egg. Transfer the egg-pudding mixture to the saucepan with the remaining pudding.
Return the pudding to low heat and cook, whisking constantly, until it just begins to bubble. Remove from the heat, whisk in the vanilla extract and salt, then divide between 4 parfait glasses. Chill for at least 1 hour. Just before serving, top each cup with shaved chocolate.