Pop your popcorn and set aside. Grease a 13 x 9 x 2 inch pan and set aside.
In a large pot, combine the corn syrup, sugar and peanut butter. Place the pan over medium heat, and bring this mixture to a boil while stirring constantly. (Seriously, stir constantly. Otherwise, you will have a burned mess on your hands.)
Lower the heat to low. (This helps prevent scorching.) Over low heat, boil your sauce for three minutes. Continue to stir the whole time.
After three minutes, remove the pan from the heat and add your popped popcorn into the pan.
At this point, please be careful, because the mixture is VERY HOT. Stir the popcorn and sauce with a wooden spoon to coat everything well.
Carefully scoop the popcorn into your greased pan and press it down so that it's flat and even in the pan. Let the popcorn cool and cut into square-shaped bars, and serve.
Serving Size 1 bar
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.