Line a sheet with parchment paper and set aside.

Pre-measure the ingredients so they're ready.

In a medium saucepan, add sugar and water and stir well. Stir in the corn syrup and cook over medium heat. Stir occassionally until it reaches a gentle boil.

Attach your candy thermometer to the side of the pan. Make sure that it is submerged but not touching the bottom. Cook until it reaches 250°F, stirring occassionally.

Add peanuts and stir constantly until it reaches 300°F.

Remove from heat and stir in butter, baking soda, and vanilla immediately. It will foam and change texture. 

Pour the mixture into the prepared pan and use a spoon to quickly and carefully spread it into an even layer. 

Cool completely before breaking apart and serving. 30 minutes minimum.