Preheat your oven to 375°F (190°C). Roll out your pie crust to fit a 9-inch pie dish. Line with parchment and add weights. Bake for 15 minutes, then remove weights and bake for an additional 5 minutes until golden.

In a medium saucepan, combine whole milk, heavy cream, ground cinnamon, and vanilla extract. Heat over medium-low until steaming. If using, steep a cinnamon stick or vanilla bean in the mixture.

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

Slowly pour the warm milk mixture into the egg mixture while whisking constantly to temper the eggs. Strain the mixture through a fine sieve into another bowl.

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

Allow pie to cool to room temperature on a wire rack for about 30 minutes. Cover with plastic wrap and refrigerate for at least 2 hours before serving.