Paula's Hot Fudge Pie

In the top of a double boiler or over low heat, melt:
1 stick butter (1/2 c.)
3 squares unsweetened chocolate
Meanwhile, beat until light:
4 eggs
Beat in:
3 T. white Karo
1 1/2 c. sugar
1/4 t. salt
1 t. vanilla
Add chocolate and mix. Pour in 9" pie pan. Bake at 350 degrees 25-30 minutes or until top is crusty and filling is still soft. Filling should shake like custard.
Good to warm before serving.