Line 2 baking sheets with silicone mats or parchment paper and set aside.
In a large sauce pan, combine sugar, corn syrup and water.
Cook over medium heat, stirring occasionally, until mixture comes to a full boil (about 10-12 minutes).
Add butter and continue cooking, stirring occasionally, until mixture reaches soft crack stage (mixture forms strands that hold shape but are pliable). This takes about 15-25 minutes.
Add peanuts and continue cooking, stirring constantly, until candy reaches hard crack stage (mixture forms strands that hold shape and break when flexed). This takes about 10-12 minutes. Remove from heat.
Stir in vanilla and baking soda.
Pour mixture immediately onto prepared sheets and spread to 1/4" thick.
Allow to cool completely.
Break into pieces.