Preheat oven to 350F. Line an 8-by-8-inch baking pan with aluminum foil and spray with cooking spray.
Melt your butter in the microwave.
To a large mixing bow, add the peanut butter, egg, brown sugar, vanilla, and blend until smooth.
Add the butter.
Add the flour and stir (BY HAND - don't blend in a mixer) until just combined but be sure not to overmix.
Add 1/2 cup chocolate chips and 1/4 cup mini chips to the batter and stir.
Pour batter in prepared pan and smooth out evenly.
With the peanut butter cups, make 4 x 4 even rows of candies and push each cup down into the batter.
Sprinkle the surface with additional chocolate chips.
Bake for about 22 to 25 minutes, or until done.
Allow bars to cool in pan for at least 1 hour before slicing and serving.