Boil on high heat in medium to deep sauce pan to firm ball stage. (Use cold water to test firm ball stage.) Do not stir.
Add unsalted peanuts and stir constantly till golden brown. Remove from heat and add vanilla and soda SEPERATELY. Stir fast and pour on a greased cookie sheet. Spread.
Cool. Then crack.
NOTE: Firm Ball Stage: Drop hot syrup into cold water and try to roll into a ball with fingers. Feels like a gum drop.