Creamy butterscotch pie with a deep, caramelized flavor and fluffy whipped topping is a nostalgic family dessert. This old-fashioned classic delivers warm, buttery sweetness in every slice.
Melt the butter in a heavy-bottomed saucepan over medium heat, then add the brown sugar. Cook, stirring constantly, until the mixture bubbles and becomes fragrant—about 3-4 minutes. Do not let it burn; reduce the heat if it gets too dark.
Gradually whisk in the cornstarch, salt, and milk. Stir constantly to dissolve the sugar completely, keeping the heat at medium-low to prevent scorching.
In a separate bowl, whisk the egg yolks. Slowly ladle about 1/2 cup of the hot butterscotch mixture into the yolks, whisking vigorously to temper them and avoid scrambling.
Pour the tempered yolks back into the saucepan. Cook the mixture over medium-low heat, whisking steadily until the pudding thickens and just bubbles—about 4-5 minutes. Remove from heat, then stir in the vanilla extract.
Pour the filling into the baked pie crust and smooth the top with a spatula. Leave to cool at room temperature for 1 hour, then chill uncovered in the refrigerator for at least 2 hours until fully set.
Before serving, spread whipped cream over the set butterscotch filling or garnish each slice individually. Cut with a clean knife for best presentation.