Combine all ingredients (EXCEPT: butter and pecans) in large 4-5 qt. heavy saucepan stirring constantly/frequently cook to 239 degrees . This should take about 20 - 25 minutes. Use a candy thermometer for accuracy. Wipe down sides of pan during the last 5-10 minutes to prevent sugar crystals from forming.
Remove from heat and add 1/2 stick butter and 1 1/2 cup pecans. Allow to cool siightly.
Beat until it loses its gloss and begins to thicken just a bit.
Pour into buttered pan (9 1/4x6 1/2, 8x8 inch or 9-inch) or drop by spoonfuls onto waxed paper. Makes about 24 1-inch pieces.
NOTE: Line pan with foil or parchment and let overhang for easy removal. Also, after fudge begins to set (approximately 10 minutes), score 1/4 to 1/2 in. deep with sharp knife to make slicing easier.