Preheat your oven to 350°F (175°C). Place the pre-made pie crust in a 9-inch pie dish and poke holes in the bottom with a fork.

Bake the crust for about 10 minutes until lightly golden.

In a medium bowl, whisk together the brown sugar, cornstarch, and salt.

In a saucepan, heat the milk over medium heat until it's steaming but not boiling.

Gradually whisk the hot milk into the dry mixture until smooth.

Return the mixture to the saucepan and cook over medium heat, stirring constantly until thickened for about 5-7 minutes.

Remove from heat and whisk in the egg yolks, vanilla extract, and butter until smooth.

Pour the butterscotch filling into the baked pie crust, spread evenly, and let it cool at room temperature before chilling in the fridge for at least 4 hours.