Preheat your oven to 350°F (175°C). Spray your pie dish with vegetable oil cooking spray.

In a bowl, mix together the chopped pecans, softened butter, brown sugar, and salt. Press this mixture into the bottom and up the sides of your pie dish to form the crust. Bake for 12-15 minutes, or until it’s lightly golden brown. Let it cool completely.

While the crust is cooling, in a saucepan, whisk together the granulated sugar, flour, and salt. Gradually whisk in the milk until it’s smooth. Cook over medium heat, stirring constantly, until the mixture thickens and comes to a boil. Reduce the heat to low and cook for another minute, still stirring.

Remove the saucepan from the heat. In a separate bowl, whisk a little of the hot mixture into the beaten egg yolks to temper them. Then, pour the egg yolk mixture back into the saucepan and whisk well. Cook over low heat for another minute, stirring constantly.

Remove from heat and stir in the unsalted butter and vanilla extract until they’re melted and smooth. Pour the butterscotch filling into the cooled pecan crust.

Cover the pie with plastic wrap, pressing it directly onto the surface of the filling to prevent a skin from forming. Refrigerate for at least 3 hours, or preferably overnight, to allow the filling to set completely.