Preheat the oven to 375°F (190°C). Roll out the pie crust and press it into a 9-inch pie dish. Line with parchment paper, fill with weights or beans, and bake for 15 minutes. Remove weights and bake for another 5 minutes until golden brown.

In a medium saucepan, combine whole milk and heavy cream over medium heat. Stir in ground cinnamon and vanilla extract, and cook until steaming but not boiling, about 5-7 minutes. If using whole spices, remove and let steep for 10 minutes.

Whisk together the eggs, granulated sugar, and a pinch of salt until pale and thickened, about 2-3 minutes.

Gradually add the warm milk mixture into the eggs while whisking continuously to temper the eggs. Strain through a fine-mesh sieve to catch any solids.

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

Cool the pie to room temperature on a wire rack, then refrigerate for at least 2 hours before serving.