Line a 9x9 inch square pan with foil or parchment paper. After that, spray lightly with nonstick cooking spray.
In a large bowl, using a mixer, beat together peanut butter, butter, vanilla, salt, and 2 cups of powdered sugar, beat until smooth and a bit crumbly.
Text the mixture with your fingers, you should form a ball easily without it falling apart. If needed, add the remaining ½ cup of powdered sugar.
Place chocolate chips and shortening in a microwave-safe bowl. Heat in 30-second increments, stirring between each, until fully melted and smooth.
Arrange half of the graham cracker sheets on the bottom of the prepared pan in a single layer.
Spread 1/3 of the melted chocolate on top.
After that, add the peanut butter mixture, flatten it using your hands and make it one even layer.
Spread another 1/3 of the chocolate mixture on top of the peanut butter, then add another layer of graham cracker sheets. Top with the remaining chocolate.
Chill to set for at least 1 hour.
Slice into bars and serve.