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.
Avoid over-cooking.
Serve plain or with vanilla ice cream.
For variety, one cup of chopped pecans may be added.