Chuck Cady's Butterscotch Pie

1 cup brown sugar
1/4 cup corn starch
1/2 teaspoon salt
1 cup water
1 2/3 cups milk
1/3 cup butter or margarine
3 egg yolks slightly beaten
1 1/2 teaspoons vanilla
1 – 9 inch baked pie shell

Mix the sugar, corn starch and salt in a large sauce pan; stir in the water and milk. Add the butter then bring to a boil over medium heat, stirring constantly. Boil for 1 minute and remove from heat. Beat the egg yolks in a glass bowl then add about 1/4 of the mixture to the egg stirring quickly. Pour this back into the mixture in the sauce pan. Return to medium heat and cook and stir for one minute more. Remove from heat and add the vanilla. Set aside to cool slightly stirring once in a while. Put in the baked pie shell and top with meringue, whipped cream or cool whip. Or eat it plain!!