In a medium sized bowl, microwave the dark chocolate and coconut oil for 30 seconds at a time until melted. Stir.
Remove the muffin tin from the freezer. Roll the dough into little balls and place on the frozen chocolate. Pat down with your fingers to flatten a bit. Pour the remaining chocolate over the filling. Freeze for 10 minutes.
You can set the no bake peanut butter cups in the freezer and keep them in the fridge so they don’t melt. Then, after the recipe is hardened, you can pop them out of the muffin tins and store them in a resealable bag in the fridge or freezer.