Place the rest of the butter (that you used to grease the pan with) along with the other stick of butter and place them into a large microwave-safe bowl. Microwave for 30 seconds. Continue to microwave in 15-second intervals until melted.
Into the bowl with the melted butter add the powdered sugar, graham cracker crumbs, and peanut butter.
Stir until combined well.
Immediately spread peanut butter mixture into the greased baking dish and smooth it out. Place it in the freezer for 30 minutes to set.
While the peanut butter layer sets in the freezer, place the chocolate chips into a microwave-safe bowl. Microwave in 15-second intervals, stirring each time until the chocolate is melted and smooth, do not overcook.
Spread the melted chocolate on top of the peanut butter mixture.
Place it back into the freezer until the chocolate is just set but not frozen, about 10-15 minutes. If they're totally frozen, it's too hard to cut into bars.
Cut immediately into squares and serve.
Video
Notes
These bars need to be refrigerated at all times. If they come to room temperature, they don't hold up together too well.
Creamy peanut butter is used for these but you can use chunky if you like. I think it would be a great substitute.
I used semi-sweet chocolate chips but you could also use milk chocolate or dark chocolate chips.
If you can't find pre-packaged graham cracker crumbs, just crush up some regular graham crackers in a baggie or food processor.
You can absolutely double this recipe to make more for larger crowds because they do go fast!
If chocolate is overcooked in the microwave, the chocolate will seize. This means it will get clumps in it and won't be spreadable. If you are concerned about this, you can melt the chocolate in a double broiler. Stick a heat-safe bowl (preferably metal or a high temperature-safe glass bowl) over a pot of boiling water. Make sure the bowl fits comfortably on top of the pot without falling in. Put the chocolate chips into that top bowl and whisk constantly until melted. Then continue with the rest of the recipe.