Take a 15x10x1" cookie sheet and line with wax paper.
Pour chocolate chips into a medium sized bowl and microwave for 45 seconds, stir, then return to the microwave for 30 seconds. Stir until completely melted and smooth (you may need to throw it back into the microwave for another 30 seconds- it really just depends on the strength of your microwave).
Pour melted chocolate onto prepared sheet.
Using a flat spatula, spread chocolate out on wax paper until it's about 1/4" thick.
Sprinkle Reese's peanut butter cups, Reese's pieces, and peanuts evenly over the melted chocolate.
Place peanut butter in a small bowl and microwave for 30 seconds. Remove and stir until runny. Using a spoon, drizzle melted peanut butter over the bark.
Place bark in the fridge for 30-45 minutes so that it can set up.
When it has hardened, remove from fridge and use a sharp knife to chop into large pieces (or you can use your hands to break it into small pieces).