In a mixing bowl, stir together the melted butter, graham cracker crumbs, powdered sugar, and 1 cup of peanut butter.
Line an 8×8 square baking pan with parchment paper and add this peanut butter mixture to the pan, smoothing in an even layer.
In a microwave safe bowl, add the chocolate chips and remaining peanut butter. Microwave in 30-second increments, stirring in between, until the mixture is melted.
Pour the chocolate over the top of the peanut butter mixture, smoothing into an even layer. If using sea salt, sprinkle it on top now.
Refrigerate until set, about 2 hours or overnight. Then slice into bars and enjoy!
Notes
The easiest way to crush graham crackers into crumbs is to put them in a ziplock bag and use a rolling pin to smash/roll them into crumbs.You can also melt the chocolate chips and peanut butter in a double boiler on the stove top if you prefer.If you don’t have an 8×8 square baking pan or something similar in size, you could also divide the batter and chocolate topping into a standard (12) muffin tin for individual peanut butter cups. Just be sure to grease the pan well as parchment won’t easily work for this kind of pan.