Line a 9"x9” or 8"x11" baking pan with foil, extending foil slightly over edges.
In a large saucepan combine sugar and corn syrup. Cook over medium-low heat, stirring constantly, until sugar is dissolved. Stir in peanut butter until melted. (It only takes a couple of minutes to melt.)
Remove from heat and add cereal, stirring until combined. Press into prepared pan.
Melt chocolate chips and butter on medium power in the microwave, stirring after every 30-45 seconds. Spread melted chocolate over cereal mixture.
Chill about 30 minutes, or until chocolate is set. Lift squares out of pan with foil. Peel off foil and cut into squares.
Recipe by Hidden Ponies at https://hiddenponies.com/2012/12/saturday-sweets-peanut-butter-rice-krispie-squares/