To make the filling, mix the peanut butter with the powdered sweetener.
Scoop the mixture to form 8 discs of about 1 tablespoon each onto wax paper; freeze for at least 30 minutes.
While the discs freeze, make the cookies. Use a mixer to cream the peanut butter and the butter on medium speed. Add the erythritol, mix; add the egg and mix. Add the Keto Chow, baking powder, and cocoa powder. Mix again.
Turn out dough onto wax paper and make 16 equal portions of about 1 tablespoon, then flatten each into a disc. Sandwich the frozen peanut butter discs between two chocolate discs. Pinch the sides together to seal and place on an ungreased cookie sheet.