Preheat your oven to 375°F (190°C). Roll out your pie crust into a 9-inch pie dish, and line the crust with parchment paper and pie weights. Bake for 15 minutes, remove weights, bake for an additional 5 minutes.

In a medium saucepan, combine whole milk and heavy cream, then add ground cinnamon and vanilla. Heat over medium until steaming, being careful not to boil. If using whole cinnamon sticks, steep for about 10 minutes.

In a separate bowl, whisk the eggs and granulated sugar until smooth. Slowly add the hot milk mixture to the eggs while stirring continuously to temper the eggs. Strain through a fine-mesh sieve into another bowl.

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

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