FOR FUDGE: Combine butter, evaporated milk, sugar and salt in medium, heavy-duty saucepan. Bring to a full rolling boil over medium heat, stirring constantly. Boil, stirring constantly, for 4 or 5 minutes. Remove from heat. Add marshmallows, morsels, peanut butter, and vanilla extract; stir vigorously for 1 minute or until marshmallows and morsels are completely melted. Pour over crust. Sprinkle nuts over fudge, press in slightly. Refrigerate until set. Cut into squares.