Preheat your oven to 375°F (190°C). Roll out your pie crust to fit a 9-inch pie dish. Press it gently into the dish, line with parchment paper or aluminum foil, and fill with weights. Blind-bake for 15 minutes, then remove weights and bake for an additional 5 minutes until golden.

In a medium saucepan, combine whole milk and heavy cream, then add ground cinnamon and vanilla extract. Warm over medium heat until steaming, about 5 minutes. If using whole spices, let them steep before removing them.

In a mixing bowl, whisk together eggs, granulated sugar, and salt until pale and creamy, about 2-3 minutes.

Slowly pour the heated cream mixture into the egg mixture while whisking continuously to prevent scrambling. Strain the mixture for a smooth texture if desired.

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

Let the pie cool at room temperature for about 30 minutes, then refrigerate for at least 2 hours before serving.