Prepare an 8" x 8" pan with cooking spray, set aside.
In a large microwave save bowl melt the butter for 1 minute.
Add the marshmallows and stir to coat, return to the microwave for 1 minute.
Remove the bowl carefully and add a few drops of yellow food coloring, 1 drop of blue food coloring and 1 teaspoon of vanilla, stir the mixture until smooth.
Add the crispy rice cereal and stir to coat completely.
Press the mixture into an 8" x 8" pan and cool completely.
In a microwave safe bowl heat the heavy cream for 45 seconds, remove carefully and stir in the 1/3 c semisweet chocolate until smooth.
Spread the chocolate ganache over the top of the rice krispie treats and place in the refrigerator for 20 minutes, until set.
Remove the treats from the refrigerator and slice into 16 bars.
In a small bowl stir together the powdered sugar and milk until smooth.
Lay each bar on its side and using a tooth pick make two eyes with the white icing and place a miniature chocolate chip in the center of each eye, then using another tooth pick draw on a chocolate mouth, repeat until all bars are decorated.
Let sit 10 minutes to dry, then serve.
Recipe by It Bakes Me Happy at https://itbakesmehappy.com/2015/10/frankenstein-rice-krispie-treats.html