Preheat your oven to 350°F (175°C).

Roll out your pie crust according to package instructions and bake it until golden brown, usually around 10-15 minutes.

In a saucepan, combine the milk, heavy cream, and sugar. Heat over medium-low until warm, but do not boil.

In a separate bowl, whisk together the egg yolks, cornstarch, vanilla extract, cinnamon, and salt until smooth.

Slowly pour the warm milk mixture into the egg mixture while whisking continually.

Return the mixture to the saucepan, cooking over medium heat while stirring consistently until thickened, about 5-7 minutes.

Stir in the butter until melted and combined.

Pour the prepared custard into the baked pie crust, smoothing the top with a spatula.

Allow the pie to cool at room temperature, then chill in the refrigerator for at least 2 hours before serving.