1 cup packed brown sugar
1/4 cup cornstarch
1/2 teaspoon salt
2 1/2 cups whole milk
4 large egg yolks
3 tablespoons unsalted butter
1 teaspoon vanilla extract
Whipped cream (optional, for topping)
Extra butterscotch chips or caramel sauce for garnish (optional)

Directions:

In a medium saucepan, whisk together the brown sugar, cornstarch, and salt.
Slowly add the milk, whisking constantly to avoid lumps. Cook over medium heat, stirring frequently, until the mixture thickens and begins to bubble, about 5–7 minutes.
In a separate bowl, whisk the egg yolks. Gradually pour about 1/2 cup of the hot mixture into the yolks, whisking constantly to temper the eggs.
Pour the tempered egg mixture back into the saucepan and continue cooking for another 2–3 minutes, stirring constantly, until thick and smooth.
Remove the pan from heat and stir in the butter and vanilla extract until fully incorporated.
Pour the butterscotch filling into the prepared pie crust, spreading it evenly.
Cover with plastic wrap, pressing the wrap directly onto the surface to prevent a skin from forming. Chill in the refrigerator for at least 4 hours, or until fully set.
Before serving, top with whipped cream and garnish with butterscotch chips or caramel sauce if desired.