Line a lipped baking sheet with foil and spray with non-stick spray. Set aside.
To a medium saucepan, add the sugar, corn syrup, and water. Add in the candy thermometer to the pan making sure it touches the mixture but not the bottom of the pan. Bring the mixture to a boil over medium heat and then continue to boil until the mixture is golden brown and reaches 340 degrees. This should take about 15 minutes.
Remove the pan from the heat and quickly stir in the butter and baking soda until smooth. Then stir in the peanuts until evenly distributed.
Pour the mixture onto the prepared baking sheet and spread evenly with a silicone spoon, working quickly, as it will start to set.
Let harden at room temperature, about 30 minutes, and then break up into pieces.
Store in an airtight container.
Notes
Use a candy thermometer to make sure your sugar mixture reaches 340 degrees. Hook the thermometer to the side of the pan so it touches the mixture but not the bottom of the pan. Store in an airtight container.