01 - Preheat oven to 350°F. Place unbaked pie crust in a 9-inch pie pan. Crimp or trim edges as desired.
02 - In a medium saucepan, combine whole milk and heavy cream. Warm over medium heat until steaming, without boiling. Remove from heat.
03 - In a mixing bowl, whisk eggs, granulated sugar, cornstarch, vanilla extract, ground cinnamon, and salt until smooth and well combined.
04 - Gently pour the warm milk mixture into the egg mixture, whisking constantly to temper and incorporate.
05 - Strain the custard using a fine-mesh sieve into a clean bowl to ensure a silky consistency.
06 - Pour the prepared custard filling into the pie crust.
07 - Bake for 45 to 50 minutes, or until the center is set but still slightly wobbly. Tent crust edges with foil if browning too quickly.
08 - Remove from oven and place on a wire rack to cool. Custard will continue to set as it cools.
09 - Sprinkle the surface with ground cinnamon and, if desired, dust with powdered sugar. Chill in the refrigerator at least 2 hours before slicing and serving.