Sprinkle on the finely crushed Oreo cookie crumbs and toss to combine then add in the larger pieces of Oreos and toss to combine. You want to do this all quickly so the Oreo can stick to the melted white chocolate.
Pour the popcorn onto two lined sheet pans, you can use a Silpat liner or parchment paper or wax paper, and spread it out in an even layer to cool and set.