Step 1: Prepare the Crust

1. Preheat the oven to 350°F (175°C).
2. In a medium bowl, combine chopped pecans, softened butter, brown sugar, and salt (if using).
3. Press the mixture into a 9-inch pie dish, covering the bottom and sides evenly.
4. Bake for 10 minutes or until golden brown and fragrant. Remove from oven and let cool.

Step 2: Make the Butterscotch Filling

5. In a medium saucepan over medium heat, whisk together brown sugar, cornstarch, flour, butter, and salt.
6. Once melted and bubbly, slowly pour in the condensed milk-water mixture, whisking continuously.
7. Keep stirring for 3-5 minutes until the mixture thickens.
8. Remove from heat and slowly stir in beaten egg yolks, whisking continuously to prevent scrambling.
9. Return to heat for 2 more minutes, stirring constantly.
10. Remove from heat, add vanilla extract, and stir well.
11. Pour the butterscotch filling into the cooled pecan crust.

Step 3: Chill & Serve

12. Allow the pie to cool to room temperature, then refrigerate for at least 2 hours to set.
13. Before serving, top with whipped cream and enjoy!