Place popcorn in a large bowl or on a large cookie sheet....in my experience the bowl would probably be better.
In a heavy saucepan combine sugar and karo syrup. Bring mixture to a boil stirring constantly. Allow to boil for 1 minute.
Remove from heat and stir in peanut butter and vanilla. Immediately pour over popcorn and stir to coat.
Chocolate Topping
In a microwave safe bowl place chocolate chips and 1 TBSP Peanut Butter. Microwave at 50% power for 30 seconds;stir. Continue until melted to a pouring consistency.