01 - Preheat oven to 350°F. Position unbaked 9-inch pie crust in pie pan and shape edges as desired.
02 - Combine whole milk and heavy cream in a medium saucepan. Heat over medium until steaming, not boiling. Remove from heat.
03 - In a mixing bowl, vigorously whisk together eggs, granulated sugar, cornstarch, vanilla extract, ground cinnamon, and salt until the mixture is smooth.
04 - While whisking constantly, slowly pour the warm dairy into the egg mixture to combine without curdling.
05 - Pass the custard base through a fine-mesh sieve into a clean bowl to achieve a velvety texture.
06 - Pour strained custard into prepared pie crust, spreading evenly.
07 - Bake on center rack for 45 to 50 minutes, until custard is set but center slightly jiggles. Shield crust with foil if needed to prevent excessive browning.
08 - Remove from oven and allow to cool on a wire rack. Custard will firm up as it cools.
09 - Dust with ground cinnamon and powdered sugar if desired. Refrigerate at least 2 hours before slicing.