Roast pistachios on a baking tray for 5-7 minutes, until fragrant. Remove from tray and set aside. Allow time to cool.
Line a baking tray with parchment paper (or foil).
Melt chocolate in the top of a double boiler on medium low heat, stirring often. Let cool to room temperature. Stir cranberries and pistachios into melted chocolate, reserving a few to sprinkle on the top if desired.
Pour bark mixture onto the lined baking tray. Refrigerate for one hour or until chocolate is completely hardened. Break into pieces.
Notes
Makes about 1 ½ pounds.
Refrigerate white chocolate bark in a parchment-lined container because it is temperature sensitive and will melt quickly if left at room temperature.