01 - Preheat oven to 350°F (175°C). Place the unbaked pie crust in a 9-inch pie pan, shaping and trimming edges as desired.
02 - In a medium saucepan, gently heat the whole milk and heavy cream over medium heat until steaming, avoiding a boil. Remove from heat.
03 - In a mixing bowl, vigorously whisk together eggs, granulated sugar, cornstarch, vanilla extract, ground cinnamon, and fine sea salt until completely smooth.
04 - Gradually pour the warm dairy into the egg mixture, whisking constantly to temper and incorporate without curdling.
05 - Pass the custard mixture through a fine-mesh sieve into a clean bowl to ensure a silky texture.
06 - Pour the strained custard filling evenly into the prepared pie crust.
07 - Bake for 45–50 minutes or until the custard is just set in the center with a slight wobble. Tent crust edges with foil if browning too quickly.
08 - Remove from oven and place on a wire rack to cool, allowing the custard to firm up as it cools.
09 - Sprinkle the top with ground cinnamon and, if desired, dust with powdered sugar before serving.
10 - Refrigerate for at least 2 hours prior to slicing and serving.