Line a baking tray with silpat or parchment paper.
Roughly chop the pistachio and cranberries. Keep aside.
Place the dark chocolate in a large heat proof bowl. Place that bowl atop a saucepan of hot water. Keep stirring the dark chocolate till it melts.
You can also melt chocolate in the microwave in 30 second increments.
Once melted, pour the chocolate over the lined tray. Spread evenly.
Now melt the white chocolate ( if using) in the double boiler or microwave.
Pour the white chocolate over the dark chocolate and using a wooden skewer, gently create swirls.
Sprinkle on all the toppings evenly all over the surface.
Transfer to the refrigerator for at least 2 hours to cool.
Once completely set, break into rough bite sized pieces. Enjoy!!