01 - Preheat the oven to 350°F. Place the unbaked pie crust into a 9-inch pie pan and form the edges as desired.
02 - In a medium saucepan, combine the whole milk and heavy cream. Warm over medium heat until steaming but not boiling, then remove from heat.
03 - In a mixing bowl, whisk together the eggs, granulated sugar, cornstarch, vanilla extract, ground cinnamon, and fine sea salt until smooth.
04 - Gradually pour the warm milk and cream into the egg mixture, whisking constantly to prevent curdling and ensure thorough blending.
05 - Strain the custard through a fine-mesh sieve into a clean bowl for a velvety consistency.
06 - Pour the strained custard filling into the prepared pie crust.
07 - Bake for 45 to 50 minutes, or until the center is just set but still slightly wobbly. Tent the crust edges with foil if they brown too quickly.
08 - Transfer pie to a wire rack and cool completely to allow the custard to finish setting.
09 - Sprinkle the top with ground cinnamon and, if desired, lightly dust with powdered sugar before serving.
10 - Refrigerate the pie for at least 2 hours before slicing to ensure clean, stable slices.