In a large thick bottomed pot, over medium heat, melt butter.
Once butter is melted, add 3/4 the bag of marshmallows.
Stir, and keep an eye on it, do NOT let it come to a boil.
Remove from heat.
Add your crispy rice cereal, and stir it all together.
Add in the remaining marshmallows.
Spray a 9x13 casserole dish with non-stick spray, and pour the rice krispie treat mixture into pan, and using your hand, press it into the pan evenly.
Let sit for 30 minutes, then cut into 18 even sized bars.
Melt your chocolate in the microwave in 30 second intervals
Dip each bar into the chocolate and then press a Butterfinger Peanut Butter Cups Skulls Fun Sized
Let chocolate set, and enjoy!