Place semisweet chocolate in microwave-safe 8-cup measuring cup or large bowl. Place white chocolate in microwave-safe 2-cup measuring cup or medium bowl. Heat semisweet chocolate in microwave, covered with waxed paper, on High 2 to 3 minutes or until almost melted, stirring once. Remove from microwave and stir until smooth. Heat white chocolate in microwave, covered with waxed paper, on High 1 to 2 minutes or until almost melted, stirring once. Remove from microwave and stir until smooth.
Stir 1 cup pistachios and 1 cup cherries into semisweet chocolate. On large cookie sheet, spread chocolate mixture to about 1/4-inch thickness. Spoon dollops of white chocolate onto semisweet-chocolate mixture. With tip of knife, swirl chocolates together for marbled look. Sprinkle with remaining pistachios and cherries.
Refrigerate bark 1 hour or until firm. Break bark into pieces. Store in tightly sealed container in refrigerator up to 1 month. Pack in decorative boxes lined with waxed tissue paper or colored cellophane for gift giving.