Line a 9x9-inch or 9x13-inch pan with foil and spray with cooking spray. (Or you can use any size pan in between; the bigger the pan the thinner the bars.)
Place melted butter, Ritz cracker crumbs, powdered sugar, and 3/4 cup peanut butter in a large bowl. Mix by hand until combined. Press firmly into prepared pan.
Place chocolate chips and remaining 2 tablespoons peanut butter in a microwave-safe bowl. Heat on 50% power in 30 second increments, stirring between each, until melted and smooth. Pour over bars and spread with a spatula to evenly coat.
Chill for at least 1 hour to set, slice into bars. **It’s best to slice them at room temperature so your chocolate doesn’t shatter.**
These can be stored in an airtight container at room temperature or in the refrigerator, depending on how warm your house is. The chocolate will get melty if it’s too hot, so use your judgement on where you should store them.