01 - Preheat oven to 350°F. Arrange the unbaked pie crust in a 9-inch pie pan and crimp or trim the edges as desired.
02 - In a medium saucepan, combine whole milk and heavy cream. Heat gently over medium setting until steaming, ensuring the mixture does not come to a boil. Remove from heat.
03 - In a mixing bowl, whisk together eggs, granulated sugar, cornstarch, vanilla extract, ground cinnamon, and salt until mixture is smooth.
04 - Slowly stream the warm milk and cream into the egg mixture, whisking continuously to prevent curdling and achieve a homogenous custard.
05 - Pour the custard through a fine-mesh sieve into a clean bowl to ensure a silky-smooth consistency.
06 - Gently pour the strained custard filling into the prepared pie crust.
07 - Bake in the preheated oven for 45 to 50 minutes, or until the custard is set but slightly wobbly in the center. If the edges of the crust brown too quickly, shield with foil.
08 - Remove the pie from the oven and allow it to cool on a wire rack. The custard will continue firming as it cools.
09 - Sprinkle ground cinnamon over the cooled pie and dust with powdered sugar if desired. For optimal texture, chill the pie in the refrigerator for a minimum of 2 hours before slicing.