Microwave 1 cup white chocolate chips with 1 tablespoon shortening in a microwave-safe bowl, stirring every 30 seconds, until melted, 2 to 3 minutes. Repeat in a separate bowl with 1 cup semisweet chocolate chips and 1 tablespoon shortening. Spread 6 cups popcorn on a baking sheet and drizzle with both chocolate mixtures. Sprinkle with 1/4 cup roughly chopped peppermint candies and a pinch of kosher salt. Let harden, about 1 hour, then break into pieces.