Preheat your oven to 400°F (200°C).

Prick the pie crust multiple times then bake for about 10 minutes until lightly golden brown. Allow it to cool.

In a saucepan, whisk together whole milk, granulated sugar, cornstarch, vanilla extract, and salt. Cook over medium heat, stirring, until it thickens (5-7 minutes).

Remove from heat, stir in diced butter until melted and smooth.

Reduce oven temperature to 350°F (175°C). Pour the filling into the crust and bake for 10 minutes or until bubbling.

Cool on a wire rack at room temperature, then chill in the refrigerator for at least 8 hours.

Sprinkle cinnamon on top before serving.