Place 1 cup of water in the bottom of a double boiler. Place 1 1/2 cups of white chocolate in the top pan. Heat the water over medium-low heat and allow the white chocolate to melt, stirring often. Once the white chocolate has melted, take the pan off the heat and stir in the remaining 1/2 cup white chocolate. Stir until all of the white chocolate is melted. Let the chocolate sit for 5 minutes to cool a bit.
Cover a small baking sheet with wax paper. Pour the chocolate onto the wax paper and spread it into an 8-10" square. Immediately sprinkle the chopped candied cherries and pistachios on top of the white chocolate. Press the cherries and nuts in gently.
Place the pan in the refrigerator to allow the chocolate to set. This will take about 15-20 minutes.