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. Warm over medium heat until steaming, without allowing to boil. Remove from heat.
03 - In a mixing bowl, whisk together eggs, granulated sugar, cornstarch, vanilla extract, ground cinnamon, and fine sea salt until smooth.
04 - Gradually pour the warm dairy mixture into the egg mixture, whisking constantly to temper.
05 - Pour the custard base through a fine-mesh sieve into a clean bowl to achieve a smooth consistency.
06 - Transfer the strained custard filling into the prepared pie crust.
07 - Bake for 45 to 50 minutes or until the center is set yet slightly wobbly. Shield the crust edges with foil if browning too quickly.
08 - Remove from oven and cool on a wire rack. The custard will further set during cooling.
09 - Sprinkle with ground cinnamon and, if desired, dust with powdered sugar. Refrigerate at least 2 hours before slicing and serving.