In a small bowl, separate 1 egg white from the yolk, reserving both. Lightly beat the egg white.
Prepare the crust.
Brush the unbaked pie crust with the beaten egg white.
Prebake the crust.
Place the crust in the preheated oven and bake for 7 to 8 minutes. Remove from the oven and allow the crust to cool for 10 minutes.
Prepare the custard filling.
In a large mixing bowl, whisk together 3 whole eggs, the reserved egg yolk, any remaining beaten egg white, sugar, salt, vanilla extract, heavy cream, and milk until smooth and fully combined.
Fill the pie crust.
Pour the custard mixture into the cooled prebaked pie crust.
Add the nutmeg.
Sprinkle the top of the custard evenly with nutmeg.
Bake the pie.
Bake for 35 to 45 minutes, or until a knife inserted in the center comes out clean and the custard is set.
Cool the pie.
Remove the pie from the oven and place it on a wire rack to cool completely.
Chill and store.
Once cooled, refrigerate the pie until ready to serve. Store leftovers in the refrigerator.
Notes
To make this recipe gluten-free, use a certified gluten-free 9-inch pie crust.Confirm that the vanilla extract, nutmeg, sugar, salt, eggs, milk, and heavy cream are gluten-free and free from cross-contamination warnings.If using a store-bought gluten-free pie crust, follow the package directions for prebaking, as baking times may vary.Use clean bowls, whisks, measuring cups, and baking tools to avoid cross-contamination.Allow the gluten-free crust to cool slightly before adding the custard filling to help prevent sogginess.Store the finished pie in the refrigerator and cover it loosely to protect the custard texture.