Melt the two chocolates in a heatproof bowl set over a pan of simmering water.
Meanwhile, line a sheet pan with parchment paper. Using a ruler and a pencil, draw a 9-by-10-inch rectangle on the paper. Turn the paper face-down on the baking sheet.
Pour the melted chocolate over the paper and spread to form a rectangle, using the outline. Sprinkle the cashews, apricots and cranberries over the chocolate. Set aside for 2 hours until firm. Cut the bark in 1-by-3-inch pieces and serve at room temperature.