Combine chocolate chips, peanut butter, and 2 tablespoons heavy whipping cream in a microwave-safe bowl. Heat on high power for 30 seconds. Let sit in microwave for 2 minutes, then stir. Microwave for 15 more seconds, then stir until completely smooth. Stir in the remaining 1 tablespoon of heavy whipping cream and drizzle chocolate mixture over the top of the monster cookie bars.