Preheat the oven to 375°F (190°C).

Place the unbaked pie crust into a 9-inch pie dish and set it aside.

In a medium saucepan, combine the whole milk, heavy cream, sugar, salt, vanilla extract, cinnamon, and nutmeg. Stir over medium heat until the mixture is hot but not boiling.

In a separate bowl, whisk together the eggs and cornstarch until smooth.

Gradually add a small amount of the hot milk mixture into the beaten eggs to temper them, whisking constantly to avoid curdling.

Slowly pour the egg mixture back into the saucepan with the remaining milk mixture, whisking continuously.

Continue to cook over medium heat, stirring constantly, until the custard thickens (5-7 minutes).

Once thickened, remove the custard from the heat and pour it into the prepared pie crust.

Smooth the top with a spatula, then sprinkle lightly with extra nutmeg or cinnamon if desired.

Bake for 40-45 minutes, or until the custard is set and the top is golden brown.

Let the pie cool completely before slicing. Serve chilled or at room temperature.