Preheat your oven to 375°F (190°C). Fit your pie crust into a 9-inch pie dish and blind-bake for 15 minutes using pie weights. Then bake for an additional 5 minutes until golden brown.

In a medium saucepan, combine whole milk, heavy cream, ground cinnamon, and vanilla extract. Heat over medium until aromatic. Do not boil.

In a large bowl, whisk eggs and granulated sugar until pale and frothy, about 2-3 minutes. Ensure sugar is fully dissolved.

Gradually pour the warm milk mixture into the egg mixture while whisking continuously to avoid scrambling. Strain through a fine-mesh sieve to remove lumps.

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

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