Preheat your oven to 375°F (190°C). Roll out your pie crust into a 9-inch pie dish, ensuring it fits snugly. Line the crust with parchment paper and fill with pie weights. Bake for 15 minutes, then remove weights and continue baking for an additional 5 minutes until golden brown. Let cool.

In a medium saucepan, combine whole milk and heavy cream, adding ground cinnamon and vanilla extract. Heat gently over medium until steaming but not boiling. If using a cinnamon stick or vanilla bean, steep for 10 minutes. Remove from heat and cool slightly.

In a mixing bowl, whisk together the eggs and sugar until pale and slightly thickened, about 3 minutes.

Slowly pour the warm milk mixture into the egg-sugar mixture, whisking constantly. Strain through a fine-mesh sieve into a clean bowl.

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

Cool at room temperature for about an hour. Refrigerate for at least 2 hours or overnight before serving.