This fudge was one of my childhood favorites. It came to my maternal grandfather from his parents. I recommend against using margarine in the place of butter. I always use butter for cooking. I’m very interesting in hearing from those of you who try it.
Combine first 6 ingredients in stovetop cooking pot and stir constantly over low heat until all ingredients are well blended. Insert candy thermometer and simmer, stirring occasionally until mixture reaches 238 degrees Fahrenheit or 114.4 degrees Celsius. Turn off heat and add butter (do not mix). Let stand until it cools to 110 degrees Fahrenheit or 43.3 degrees Celsius. Add vanilla, remove thermometer and stir vigorously until glossiness fades. Fold in broken walnuts and pour into a well buttered pan. Cut into bite-size squares as soon as possible.
NOTE: If fudge hardens too quickly, add 1 tablespoon cream or milk and reheat over low heat until it can be properly stirred. Pour into buttered pan immediately.