Preheat your oven to 375°F (190°C). Roll out your pie crust and place it in a 9-inch pie dish. Line with parchment paper and fill with baking weights or dried beans. Bake for 15 minutes, then remove weights and parchment and bake for an additional 5 minutes until lightly golden. Let cool slightly.

In a saucepan, combine whole milk, heavy cream, ground cinnamon, and vanilla extract (or steep cinnamon stick/vanilla bean). Heat over medium until steaming but not boiling, steep for 10 minutes if using sticks.

In a mixing bowl, whisk together eggs, sugar, and a pinch of salt until smooth. Gradually pour in the warm milk mixture while whisking continuously to temper the eggs. Strain the mixture through a fine-mesh sieve into another bowl.

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

Allow the pie to cool at room temperature before refrigerating for at least 2 hours.