How to Make It
Finely crush the cookies using a food processor.
Line the bottom and sides of a square pan with parchment paper and lightly grease it with cooking spray. Press the crushed cookies into the bottom of the pan in an even layer and freeze while you complete the next few steps.
Combine the marshmallow cream and cream cheese in the bowl of a stand mixer. Use the whisk attachment to beat over high speed for 2 minutes. Fold in 1 cup sprinkles.
Remove pan from freezer, and spread mixture over top of the cookie layer. Chill overnight.
Sprinkle with remaining rainbow sprinkles and slice.