1) In 4 quart duct oven, stir together sugar, milk, water, cocoa, corn syrup, and salt. Cook over medium heat (do not turn heatup), stirring occasionally until it comes to a boil.
2) Once it comes to a boil, continue cooking but DO NOT stir again.
3) Continue cooking until it reaches soft ball stage on candy thermomenter (235 degrees) or until a small amount dropped into cold water forms a soft ball.
4) Remove from heat and add the butter and peanut butter. Using a wooden spoon, stir vigorously until the fudge loses its gloss and holds it shape when dropped.
5) Pour into a buttered 9 x 13" pan and let it cool.