Preheat your oven to 375°F (190°C). Roll out your pie crust into a 9-inch pie dish and carefully line it with parchment paper. Fill with pie weights or dried beans, then bake for 15 minutes. Remove the weights and parchment, and bake for an additional 5 minutes until the crust is golden brown. Allow it to cool slightly before adding the custard filling.

In a medium saucepan, combine whole milk and heavy cream over medium heat. Add ground cinnamon and vanilla extract to the mixture, stirring gently until it reaches a steaming point—do not let it boil. If you're using whole spices, let them steep in the warm mixture for about 10 minutes before removing them.

In a large mixing bowl, whisk together the fresh, room-temperature eggs with the granulated sugar and a pinch of salt until pale and smooth, about 2-3 minutes.

Slowly pour the hot milk mixture into the egg mixture, whisking continuously to avoid curdling, then strain through a fine sieve into a bowl.

Lower oven temperature to 325°F (160°C). Carefully pour the custard mixture into the pre-baked pie crust. Bake for 35-40 minutes, or until the edges are set and the center slightly jiggles when gently shaken.

Once baked, cool on a wire rack at room temperature for about 30 minutes. Refrigerate for at least 2 hours before serving.