Microwave the remaining bittersweet chocolate in a bowl at 50% power for 1 to 1 1/2 minutes. Use a spatula to scrape down the sides and stir. Continue to microwave the chocolate for 15 second intervals at 50% power, stirring between intervals, until just small lumps remain. Stir until smooth and pour into the prepared pan.
Combine the Rice Krispies and 1/2 cup of dried cranberries and mix them together. Melt the white chocolate using the same method as the bittersweet chocolate, keeping in mind that white chocolate melts at a lower temperature than bittersweet chocolate.
Gently fold the cereal mixture into the white chocolate until evenly incorporated. Spread over the bittersweet chocolate and smooth the top. Sprinkle with the remaining dried cranberries and return to the refrigerator to chill for another 30 minutes.
Melt the remaining 2 tablespoons of bittersweet chocolate and pour into a small plastic bag. Cut a small hole in the corner and drizzle the chocolate over the bark. Allow the bark to warm up slightly, about 10 minutes, and pull it out of the pan using the aluminum foil overhang and transfer to a cutting board.