01 - Preheat oven to 350°F (175°C). Place the unbaked 9-inch pie crust in a pie pan and crimp or trim the edges as desired.
02 - In a medium saucepan, combine whole milk and heavy cream. Warm over medium heat until steaming but not boiling, then remove from heat.
03 - In a mixing bowl, whisk together eggs, granulated sugar, cornstarch, vanilla extract, ground cinnamon, and salt until smooth.
04 - Slowly pour warm milk mixture into the egg mixture, whisking constantly to temper and fully blend.
05 - Strain the custard through a fine-mesh sieve into a clean bowl for a silky texture.
06 - Pour the custard filling into the prepared pie crust.
07 - Bake for 45 to 50 minutes, or until the center is set but still slightly wobbly. Cover the crust edges with foil if they begin to brown too quickly.
08 - Remove the pie from the oven and cool completely on a wire rack. The custard will continue to set as it cools.
09 - Once cooled, sprinkle the surface with ground cinnamon and lightly dust with powdered sugar if desired.
10 - Chill in the refrigerator for at least 2 hours until fully set before slicing and serving.