Line a sheet pan with a piece of parchment or waxed paper.
Place the semisweet chocolate chips in a microwave safe bowl and heat on high until most of the chips are melted, about 2 minutes. Alternatively you can put the chips in a heatproof bowl over a pan of barely simmering water (making sure the bottom of the bowl does not touch the water) and melt the chocolate. Stir until all the chips are melted and the chocolate is smooth and glossy. Add 1 cup of the pistachios to the chocolate and stir to combine. Pour onto the paper and spread into an even layer with a spatula about an eighth or a quarter inch thick.
Put the white chocolate chips in a microwave safe bowl and heat on high until they start to melt, about 1½ minutes. Alternatively you can put the chips in a heatproof bowl over a pan of barely simmering water (making sure the bottom of the bowl does not touch the water) and melt the chocolate. Stir until smooth. Drop spoonfuls of the white chocolate here and there with a spoon onto the semisweet chocolate. With a knife or back of a spoon swirl the white chocolate into the semisweet. Sprinkle the rest of the pistachios and the cranberries over the top. Let cool. Place in the refrigerator until hard, about 30 minutes. Cut or break into irregular sized and shaped pieces.