In a saucepan over moderate heat, mix together all ingredients except nuts, stirring until sugar is dissolved.
Boil, stirring constantly until mixture reaches the soft ball stage (234 degrees).
Remove from heat and cool to lukewarm without stirring. Beat until mixture thickens and is no longer glossy.
Stir in nuts and pour into buttered pie plate or dish, to a thickness of approximately 1 inch.
Refrigerate until firm.
Cut into serving pieces. Quantity varies with thickness of fudge.