01 - Preheat oven to 350°F. Position unbaked pie crust in a 9-inch pie pan, crimping or trimming edges as preferred.
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, vigorously whisk the eggs, granulated sugar, cornstarch, vanilla extract, ground cinnamon, and salt until homogeneous.
04 - Gradually pour the warm dairy mixture into the egg mixture, whisking continuously to combine and prevent curdling.
05 - Pass the custard through a fine-mesh sieve into a clean bowl to remove any lumps and ensure a smooth consistency.
06 - Pour the strained custard filling into the prepared pie crust, spreading evenly.
07 - Transfer to the oven and bake for 45–50 minutes, or until the center is set yet slightly wobbly. Shield crust edges with foil if browning excessively.
08 - Remove from oven and place on a wire rack to cool. Custard will continue to set as it reaches room temperature.
09 - Sprinkle ground cinnamon evenly over the top. Dust with powdered sugar before serving, if desired.
10 - Refrigerate for a minimum of 2 hours to ensure clean slices.