This recipe can be made with bittersweet or semi-sweet chocolate. I prefer bittersweet. I've also made it with pecans and my mom likes it with slivered almonds. Just make sure that whatever nut you use, you roast them to bring out their nutty goodness.
Bittersweet Chocolate Pistachio Bark
1 lb of bittersweet chocolate, chopped
½ cup unsalted roasted pistachios
2 to 3 pinches of grey salt
Line a cookie sheet with parchment paper. In a double boiler set over simmering water, heat the bittersweet chocolate until two-thirds melted. Remove from the heat. Stir the chocolate until it is completely melted.
Spread the warm chocolate on the parchment paper to a rough 13 inch rectangle. Scatter the pistachios evenly over the melted chocolate, gently tap the cookie sheet on the work surface to flatten the chocolate and allow the topping to sink in slightly. Sprinkle on the salt.
Refrigerate for about 15 minutes, just until firm. Cut or break the bark into 2 inch pieces and serve.