Line a 9 x 9-inch square pan with foil or parchment paper and spray with non-stick cooking spray.
In a medium bowl, with a hand mixer, beat together peanut butter, butter, salt, and 1 ½ cups of confectioners' sugar until thoroughly combined; the mixture will be crumbly; test the mixture – it should not be sticky and should form a ball easily without falling apart; if needed, add up to ½ cup more powdered sugar.
Place chocolate chips and shortening in a microwave safe bowl; heat in 30 second increments, stirring between each, until melted and smooth.
Place half the graham crackers on the bottom of the prepared pan in a single layer.
Spread ⅓ of the melted chocolate over the top.
Scoop out balls of the peanut butter mixture, flatten between your hands and place evenly over the chocolate; smooth out carefully with your fingers so it's as even as possible.
Spread another ⅓ of the chocolate mixture over the top of the peanut butter, then layer with another layer of graham crackers.
Spread the rest of the remaining chocolate over the top.
Chill to set, at least 1 hour.
Slice into bars and return to refrigerator until ready to serve.
