Preheat your oven to 375°F (190°C). Roll out your pie crust and carefully place it into a 9-inch pie dish. To prevent bubbling, line the crust with parchment paper and fill it with pie weights. Bake for 15 minutes, then remove the weights and parchment. Continue baking for an additional 5 minutes until the crust is golden brown and fragrant.

In a medium saucepan, combine whole milk and heavy cream, then stir in ground cinnamon and vanilla extract. Heat the mixture over medium heat until it begins to steam, but do not let it boil. If using a cinnamon stick or vanilla bean, steep the mixture for about 10 minutes. Remove the stick or strain out the vanilla bean to ensure a smooth custard base.

In a large mixing bowl, whisk together the eggs, granulated sugar, and a pinch of salt. Continue whisking until smooth and lightened in color, creating a rich foundation for the filling.

Once the milk mixture is hot, slowly pour it into the egg mixture while whisking continuously to temper the eggs. Strain the mixture through a fine-mesh sieve if desired for extra silkiness.

Reduce the oven temperature to 325°F (160°C). Carefully pour the custard mixture into the pre-baked crust without overflowing. Bake for 35-40 minutes, until the edges are set and the center jiggles slightly.

Once baked, allow your Cinnamon-Vanilla Custard Pie to cool at room temperature for about 30 minutes. Then cover loosely and refrigerate for at least 2 hours to enhance flavors.