Line a 9 x 9 pan with parchment paper and lightly spray with cooking spray.
Evenly space 16 peanut butter cups in the pan.
Melt the chocolate chips and condensed milk in the microwave by heating for 1 minute then stirring and repeating (probably 3-5 minutes depending on your microwave).
Spread the melted chocolate over the peanut butter cups in the pan.
Cut or break up the remaining 4 peanut butter cups and sprinkle evenly over pan, pressing lightly into the fudge.