Combine the sugar, corn syrup and water in a heavy 3-quart saucepan. Cook over medium heat, stirring constantly, until the sugar is dissolved. (Note: Be very careful when you make this recipe as the syrup is dangerous if spilled on you.) Continue cooking, stirring occasionally, until the mixture reaches the soft crack stage (285 degrees F.) on the candy thermometer. Add the peanuts and butter. Cook, stirring constantly, to the hard crack stage (300 degrees F.) on the candy thermometer. Remove from the heat. Rapidly stir in the baking soda and vanilla.

(Mixture will foam up.) Turn the mixture onto 2 greased baking sheets (Jelly roll pans work nicely).

Spread out with a metal spatula as thin as possible.

When the candy begins to set, loosen from the baking sheets. Turn the brittle over, then stretch and pull brittle as thin as possible using two forks. When completely cooled, break into pieces.

Makes about 2 pounds of brittle.