Preheat the oven to 350 deg F Spread the walnuts on a baking sheet and toast for 8 minutes, or until golden and fragrant. Let cool, then coarsely chop.
Line a baking sheet with parchment or wax paper. In a glass bowl, heat two-thirds of the chocolate in a microwave oven at high power in 30-second bursts until just melted. Stir until smooth. Add the remaining chocolate and stir until melted. Stir in the walnuts, cherries and crystallized ginger until evenly coated. Scrape the mixture onto the prepared baking sheet and spread it into a 12-by-8-inch rectangle. Refrigerate for 10 minutes, or until firm enough to cut
Cut the bark into 48 pieces (6 rows by 8 rows) and transfer to a plate. Serve cold or at room temperature.