Prep: Butter the bottom and side of an 8x8 container and set aside. Fill the sink with two inches of cold water to be used to cool down the mixture in the cooking pan.
Mix fix first 5 ingredients in pan. Cook on medium high heat using candy thermometer to monitor temperature. NOTE: The candy thermometer should be clipped on the side of the pot and not ever touching the bottom. Stir constantly to prevent sticking and/or burning. When temperature reaches 220 (just below soft ball state) remove pot from heat. Remove candy thermometer.
Add vanilla. Place bottom of pan into cold water bath and stir constantly making sure you keep the mixture moving to ensure it sets evenly. Continue this until you can create a figure 8 in the mixture that holds its form. Approx 2-3 minutes.
Remove pot from water. Stir in nuts. Pour into pre-greased 8x8 container.