01 - Preheat oven to 350°F. Arrange the unbaked pie crust into a 9-inch pie pan and trim or crimp the edges.
02 - In a medium saucepan, combine whole milk and heavy cream. Heat gently over medium, stirring, until steaming but not boiling. Remove from heat.
03 - In a mixing bowl, whisk eggs, granulated sugar, cornstarch, vanilla extract, ground cinnamon, and salt until smooth.
04 - Gradually whisk the warm milk mixture into the egg mixture, constantly whisking to prevent curdling.
05 - Pass the custard filling through a fine-mesh sieve into a clean bowl for a velvety texture.
06 - Pour the custard filling into the prepared pie crust. Transfer to the oven and bake for 45-50 minutes, until the center is set but jiggles slightly. Cover edges with foil if crust browns rapidly.
07 - Remove from oven and cool on a wire rack. Allow to set completely as it cools.
08 - Sprinkle with ground cinnamon and dust with powdered sugar if desired. Chill for at least 2 hours before slicing.