In a medium saucepan, combine the whole milk, orange peel, and cinnamon stick. Heat over medium heat until the milk just begins to simmer, then remove from heat, cover, and let steep for 15 minutes to infuse the citrus and spice flavors.

While the milk steeps, whisk the egg yolks, 1/4 cup of the granulated sugar, and the cornstarch together in a medium heatproof bowl until the mixture is pale yellow and slightly thickened.

Remove and discard the orange peel and cinnamon stick from the warm milk. Slowly pour a few tablespoons of the warm milk into the egg yolk mixture while whisking constantly to temper the eggs, then gradually whisk in the rest of the milk.

Pour the mixture back into the saucepan and cook over medium-low heat. Stir constantly with a wooden spoon or spatula, ensuring you scrape the bottom, until the custard thickens enough to coat the back of the spoon, about 5 to 7 minutes; do not let it boil.

Strain the thickened custard through a fine-mesh sieve directly into four shallow ramekins to ensure a silky texture. Let them cool to room temperature, then cover and refrigerate for at least 3 hours until completely chilled and set.

Just before serving, sprinkle the remaining 1/4 cup of sugar evenly over the tops of the custards. Use a kitchen torch to caramelize the sugar until it turns a deep golden-brown, crispy glass crust, then let it sit for 1 minute to harden before tapping with a spoon and serving.