In a microwave-safe bowl, melt white chocolate at 70% power; stir until smooth. Repeat with chocolate chips. Stir 6 tablespoons of crushed peppermint candies into each bowl. Drop white chocolate and semisweet chocolate in alternating spoonfuls onto a waxed paper-lined baking sheet.
With a metal spatula, cut through chocolate to swirl, spreading to 1/4-inch thickness. Sprinkle with remaining crushed candies. Chill until firm. Break into pieces. Store in an airtight container in the refrigerator.