Pop the popcorn, remove unpopped kernels, and spread on a lined baking sheet.
Melt the white chocolate in 20-second microwave bursts, stirring until smooth. Stir in peppermint extract if using.
Pour two-thirds of the melted chocolate over the popcorn and fold until evenly coated.
Spread the coated popcorn into an even, compact layer on the lined sheet.
Drizzle the remaining white chocolate on top and scatter with crushed candy canes, marshmallows, and sprinkles.
Let set at room temperature for about an hour, or refrigerate for 20 minutes.
Break into rustic pieces once fully set.