Divide your chocolate to 2 halves. To temper the chocolate, place 1 half of your chocolate in a microwave safe bowl, reserving 1 tbsp aside. Microwave for 50 secs, stir then microwave for another 10 secs if not completely melted. When melted, add the remaining 1 tbsp chocolate and stir it with the melted chocolate until dissolved.
Place 1 tsp of melted chocolate in your cupcake silicone molds spreading it to the edges. (If you don't have silicone molds, just place cupcake liners in a muffin/cupcake tin, grease them with a bit of oil and proceed).
Refrigerate for 10 mins or until chocolate is set and firm.
Place 1 tsp of pistachio butter in the center of each cup. Melt the remaining chocolate and temper it like you did with the first half. Cover the pistachio butter with 1 tsp melted chocolate while spreading it to the edges.
Garnish with crushed pistachios and refrigerate until chocolate is firm and enjoy!