Combine in a saucepan the brown sugar, salt, butter or margarine and milk. Cook, stirring until sugar is dissolved. Then cook without stirring until mixture forms a soft ball when a little is dropped in cold water (234 degrees F - 115 degrees C). Cool to lukewarm (110 degrees F). Put into small bowl and beat until it begins to thicken.

Add vanilla and cream and continue beating until of spreading consistency. If thicker consistency is desired, beat in a small amount of sifted confectioners' sugar. Quickly spread on cake. Sprinkle with chopped nuts if desired. Enough to frost two 8 inch layers.