Portion the chilled mixture using a small or medium cookie scoop, then use your hands to roll them into smooth balls. Place them on a wax or parchment paper lined baking sheet. Freeze the Oreo balls for an additional 15 to 30 minutes.
Melt both types of chocolate in separate bowls in the microwave at 30-second increments until fully melted. Prep all decorations. Use a fork to submerge each truffle into the melted chocolate of your choice. Let excess chocolate drip off before transferring to parchment paper. Add any sprinkles or extra Oreo crumbs right away, or let set if you want to drizzle more melted chocolate or candy melts on top.