Set out pie shell. In a large, heavy saucepan, combine ¾ cup of the brown sugar and water. Bring to a boil over medium heat, and continue cooking for about 3-1/2 minutes or until mixture is thick and bubbly. Set aside.
In a large mixing bowl, beat the eggs until frothy. Add the flour and blend until smooth. Add the remaining ¾ cup brown sugar and blend. Slowly add the scalded milk, stirring constantly.
Over low heat, reheat the sugar-water mixture until liquefied again. Pour the milk-egg mixture into it, stirring with a rubber spatula all the time. Cook over medium-low heat until mixture bubbles up and is very thick, 3 to 5 minutes.
Add salt, butter and vanilla extract. Let cool for 15 minutes, then pour into baked shell. Chill in your cellar or if you have a refrigerator until set. Frost the pie with the whipped cream topping.
Recipe by Amish 365 at https://www.amish365.com/homemade-butterscotch-pie/