Can I use a store-bought crust?
Absolutely. A baked store-bought pie crust makes this a very reasonable weeknight dessert. Just make sure it is fully baked and cooled before adding the warm filling.
How do I keep the filling from getting lumpy?
Temper the egg yolks slowly with the hot milk mixture, whisk constantly, and keep the heat at medium. If a few lumps still happen, do not panic. Strain the custard through a fine-mesh strainer before you whisk in the butter and chocolate.
Why did my filling not set?
Usually it needed a bit more cooking time or it never quite reached a real boil. Once you see big bubbles breaking the surface (the mixture should “burp” a little), keep whisking and boil for about 1 minute, up to 2 minutes depending on your stove and pan. That fully activates the cornstarch so the pie slices cleanly after chilling.
Can I make it ahead?
Yes. Make the pie (filling in crust) up to 1 day ahead. Add whipped cream the day of serving for the fluffiest topping.
Can I make it extra chocolatey?
Yes, and I support this. Use dark chocolate (60 to 70%) for the chopped chocolate portion and finish with chocolate curls or a dusting of cocoa. Note: darker chocolate will make the pie a little less sweet and a little more intense, in a good way.
Can I freeze it?
You can, but it is not my favorite for texture. Cornstarch-thickened custards are more likely to separate or get a little weepy after thawing than gelatin-set fillings. If you must, freeze the pie without whipped cream, wrapped well, for up to 1 month. Thaw overnight in the fridge and top with fresh whipped cream.