In a medium sized mixing bowl, use an electric mixer to combine the peanut butter and powdered sugar until smooth and homogenous.
In a separate bowl, melt the chocolate chips in the microwave on 20 second intervals until the chocolate is completely melted. Be sure to stir the chocolate after each interval.
Line a muffin tin with disposable liners and place a generous spoonful of melted chocolate in each liner.
Use a piping bag or Ziploc bag with a hole cut in the corner to pipe a small disc of peanut butter filling on top of the chocolate.
Spoon chocolate over each liner to cover the peanut butter and tap the tray on a table or counter to even out the layers.
Place the tray in the fridge for six hours, or until the chocolate has completely set.
Notes
I've had good luck using natural peanut butter and regular peanut butter for this recipe.
You can store these peanut butter cups in the fridge or freezer for up to 3 months in an airtight container.
If you are storing them in the freezer, I like to let them sit on the counter for a few minutes before eating them, so they aren’t too hard to bite into. If you store your peanut butter in the fridge, you will want to let it sit on the counter for about 10 minutes, so it isn’t too hard to combine the filling ingredients.
These make big peanut butter cups, you can always use a mini muffin tin with mini muffin wrappers to make a smaller peanut butter cup if you prefer, the method is the same.