Butterscotch Pie - Ruth Fletcher

1 cup brown sugar                              
1 tbsp cornstarch                                
¾ cup sugar                                         
3 tbsp flour                                          
2 eggs, separated
pinch salt
2½ cups water
1 tsp butter

Mix together the sugars.  Sift the cornstarch, flour and salt into the mixture.  Beat egg yolks well and add ½ cup of the water to the well beaten egg yolks.  Pour into sugar mixture with remaining water and boil until thick.  When thickened add butter and beat until smooth.  Pour into pie shell and chill.