Prepare an 18x13 baking sheet by greasing with butter and set aside.
In a small bowl, mix baking soda, salt and vanilla extract and set aside.
In a large heavy bottomed pot, combine sugar, corn syrup and water.
With a heat proof spoon or spatula, stir mixture constantly over very high heat until it reaches 240 degrees on candy thermometer.
Add peanuts and continue stirring until mixture reaches 320 degrees on candy thermometer.
Remove mixture from heat and stir in butter until melted.
Stir in baking soda mixture. It will be foamy, stir until combined.
Pour mixture onto baking sheet and let set until hard.
Break into pieces.
Handwritten notes from Grandma Wanda - Must be stirred constantly. Use a wooden spoon and a candy thermometer.