Make the mug cake: Whisk the peanut butter, granulated sugar, flour, baking powder and egg together in a medium bowl and then transfer to a mug. Microwave on high until puffed and set, 60 to 70 seconds. Let cool for 5 minutes.
Meanwhile, make the frosting: Mix the powdered sugar and chocolate syrup together until smooth.
Spoon the frosting over the cake. Crush a few potato chips over the top and insert a few whole chips into the frosting. Eat immediately.