In a medium saucepan, bring the milk, orange zest, cinnamon sticks, and salt to a boil, then reduce the heat to low and simmer the mixture for 3 minutes to infuse the flavors.
In a large bowl, whisk the egg yolks with the 1 cup of sugar until pale and fluffy.
Add the cornstarch and whisk until thoroughly combined.
Remove and discard the orange zest and cinnamon sticks from the milk.
Whisking constantly, gradually add the milk to the egg yolk mixture.
Return the mixture to the saucepan and bring it to a simmer over medium heat, whisking constantly, to thicken the mixture, 3 to 5 minutes.
Strain the custard into a large bowl and whisk in the vanilla.
Divide the custard between 10 five-ounce ramekins and smooth the surfaces.
Cool the custards slightly, then cover the ramekins with plastic wrap and refrigerate them until the custard is cold, at least 8 hours or up to 24.
To serve, sprinkle each ramekin evenly with 2 teaspoons of sugar.
Use a kitchen torch to melt and caramelize the sugar until browned and crusty.