Preheat your oven to 375°F (190°C). Fit your pie crust into a 9-inch pie dish, press it evenly against the sides, and line it with parchment paper and pie weights. Bake for 15 minutes, remove weights and parchment, and bake for an additional 5 minutes until golden.

In a medium saucepan, combine whole milk and heavy cream, then stir in ground cinnamon and pure vanilla extract. Heat over medium-low until steaming, about 5 minutes, adding a cinnamon stick to steep if desired.

In a large mixing bowl, whisk together eggs, granulated sugar, and salt until pale and smooth, about 2-3 minutes.

Slowly add the warm milk mixture to the egg mixture, whisking continuously. Strain the custard through a fine sieve into a clean bowl.

Pour the smooth custard into the pre-baked pie crust, lower the oven temperature to 325°F (160°C), and bake for 35-40 minutes until edges are set and center jiggles slightly.

Let the pie cool at room temperature for about 30 minutes, then cover lightly and refrigerate for at least 2 hours before serving.