Pre-bake the Crust: Roll out the pie crust into a 9-inch pie dish, fit snugly, and press into edges. Preheat oven to 375°F (190°C), place parchment paper filled with pie weights in the crust, and blind-bake for 15 minutes. Remove weights and parchment, bake for an additional 5 minutes until golden brown, and cool completely.

Prepare Custard Base: In a medium saucepan, combine whole milk, heavy cream, ground cinnamon, and vanilla extract over medium heat. Stir gently and heat until steaming, avoiding boiling. Remove cinnamon stick if used.

Whisk Eggs & Sugar: In a large mixing bowl, beat together eggs, granulated sugar, and a pinch of salt until pale and slightly thickened, about 2-3 minutes.

Temper & Combine: Gradually pour the steaming milk mixture into the egg mixture while whisking continuously. Strain the mixture through a fine-mesh sieve into another bowl.

Fill & Bake: Pour the custard into the pre-baked pie crust, spreading evenly. Reduce oven temperature to 325°F (160°C) and bake for 35-40 minutes until edges set but center is slightly jiggly.

Cool & Chill: Allow the pie to cool at room temperature for 30 minutes, then cover loosely and refrigerate for at least 2 hours.