Cover a cookie sheet with parchment paper and spray the parchment paper with cooking spray.
In a 3 quart saucepan, combine the sugar, corn syrup and water. Cook this mixture over medium heat to the soft ball stage (about 238 degrees) on a candy thermometer, stirring it only until the sugar dissolved. Add the peanuts, salt and butter. Cook the mixture to the hard crack stage (about 290 degrees) on a candy thermometer. Remove the mixture from the heat and add the vanilla and baking soda. Stir the mixture thoroughly.
Pour the mixture onto the prepared cookie sheet. Spread it to about 1/4" thick.
Let the candy cool completely before breaking the candy into pieces.
Makes about 1 to 1 1/2 pounds of peanut brittle.
The calories shown are based on the recipe being broken into 24 pieces, with 1 serving being 1 piece of brittle. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate.