In a double boiler over low heat, melt one stick of butter and two squares of chocolate.
Meanwhile, in a mixing bowl, place four eggs and beat until light.
Into the eggs, beat three tablespoons of white Karo, one and one-half cups of sugar, three-fourths teaspoon of salt and one teaspoon of vanilla flavoring.
When the chocolate and butter have slightly cooled, add to mixture in bowl.
Mix thoroughly and pour into a nine-inch pie shell.
Bake for 25 to 30 minutes at 450 degrees, or until filling is firm.
Serve plain or with vanilla ice cream.
For variety, one cup of chopped pecans may be added.