Prepare a baking tray by either coating with butter or lining with a silpat mat that has bee coated in cooking spray.
Combine the sugar, corn syrup, and water in a heavy sauce pan over high heat. Cook and stir until the sugar has dissolved. Continue cooking on high until candy thermometer reaches 290 degrees. Once it reaches 290 degrees, add the peanuts and butter. Continue cooking and stir constantly for 1 minute. Remove from heat and add baking soda and salt, then return to a medium heat stirring and cooking until desired color (caramel color).... usually takes just a of couple minutes.
Pour out onto the prepared baking sheet and spread to desired thickness. Cool completely then break up into pieces. Enjoy.
Side Note: I cleaned my spoon, pan, and candy thermometer by submerging them in the pan full of water and simmed them until they were clean.