Preparations: Butter a cookie sheet;place in warm oven to keep warm-to hot. Combine the baking soda and vanilla in a small cup and set aside.(this keeps the soda from brown flaking in your syrup).
Combine sugar,water and corn syrup in heavy saucepan.
Bring mixture to full boil over high heat, stirring until mixture appears clear.
Cook to hard crack stage- 290 degrees.(No thermometer? Fill a cup with cold water and drip a drop of the syrup into water. Feel the drop at the bottom of the cup -- if it's hard and brittle, it's ready!
Meanwhile, put the measured peanut butter and peanuts in a medium size bowl and microwave on defrost or half power to warm .
When the syrup hits 290 remove from heat and add vanilla,soda and the warmed peanut butter mixture. Combine and stir quickly.
Working quickly, pour onto a very warm - hot buttered cookie sheet; spread with large spoons or forks.