01 - Preheat the oven to 350°F. Arrange the pie crust in a 9-inch pie pan and shape the edges as preferred.
02 - Gently heat whole milk and heavy cream in a medium saucepan over medium heat until steaming but not boiling, then remove from heat.
03 - In a mixing bowl, whisk eggs, granulated sugar, cornstarch, vanilla extract, ground cinnamon, and salt until the mixture is smooth.
04 - Gradually pour the warm milk mixture into the egg mixture, whisking constantly to incorporate and temper.
05 - Pour the custard through a fine-mesh sieve into a clean bowl to ensure a silky texture.
06 - Transfer the strained custard filling into the prepared pie crust.
07 - Bake for 45 to 50 minutes, or until the center is set but still slightly wobbly. Shield the crust edges with foil if needed to prevent over-browning.
08 - Remove the pie from the oven and cool completely on a wire rack. The custard will firm as it cools.
09 - Sprinkle ground cinnamon over the top and, if desired, dust lightly with powdered sugar before serving.
10 - Refrigerate for at least 2 hours before slicing for best texture.