Use butter to thoroughly grease a large cookie sheet. Set aside.
Measure out baking soda, salt and vanilla into small bowls. Set aside.
In a large saucepan, cook corn syrup, sugar and water over medium-high heat to soft ball stage (230 degrees F), stirring occasionally. Add raw peanuts. Continue to cook, stirring frequently, to the hard crack stage (300 degrees F). As the peanuts cook, they will start to make popping, cracking or whining sounds.
Remove from heat and immediately add the baking soda, salt and vanilla. The mixture will start to foam; stir vigorously until the foaming subsides. Pour the mixture onto the prepare cookie sheet, spreading it out to the desired thickness with a wooden spoon or a rubber spatula.
Let candy cool. Once hard, break into pieces and store in a tin for up to a week.
Notes
You MUST use raw peanuts in this recipe! You won't find them by the roasted peanuts, but can usually find them over in the produce section.