Line a 9x13 cupcake tin with liners. Spray the inside of the liners with cooking spray
Place 1/2 of your chocolate chips in a microwave safe bowl and melt in the microwave for 1 minute. Do not over cook the chocolate. It is best to remove from the microwave when there are still a few pieces of chocolate not melted. You could also place the bowl on top of a pot of simmering water and stir until melted.
When your chocolate is melted, spoon the chocolate evenly in the 12 cupcake liners.
Place in fridge to let chocolate harden (should take about 10 minutes)
While your chocolate is in the fridge, take a small mixing bowl and begin to mix together the peanut butter and powdered sweetener. You may need to place in microwave for 30 seconds to make mixing easier.
Once your chocolate is done hardening, with a spoon begin to evenly put a layer of peanut butter on top of your chocolate layer. Once finished, place into the fridge for another 10 minutes.
Melt the rest of your chocolate just as before. Remove the cups from the refrigerator and evenly spoon the melted chocolate on top. Chill for 10 minutes.
Serve. See notes for storing.