Step 1: Preheat your oven to 325°F (160°C). Gently separate the kadaif pastry strands and spread them evenly on a baking sheet. Drizzle with 2 tablespoons of melted butter or neutral oil. Bake for 10-15 minutes, tossing occasionally, until golden brown and crispy. Let cool completely.
Step 2: In a medium bowl, combine the pistachio butter, powdered sugar, and a pinch of salt. Mix until smooth. If too thick, add a tiny bit of neutral oil to reach a spreadable consistency. Gently fold in the cooled, toasted kadaif pastry.
Step 3: Finely chop the chocolate. Place ⅔ of the chopped chocolate in a heatproof bowl over a saucepan of simmering water (bain-marie), ensuring the bowl does not touch the water. Stir gently until melted and reaches 115-120°F (46-49°C) for dark chocolate, or 105-110°F (40-43°C) for milk/white chocolate.
Step 4: Remove from heat and add the remaining ⅓ chopped chocolate. Stir continuously until all chocolate is melted and the temperature drops to 88-91°F (31-32°C) for dark, or 84-86°F (29-30°C) for milk/white chocolate. Your chocolate is now tempered.
Step 5: Pour about half of the tempered chocolate into your silicone chocolate bar mold. Tilt and tap the mold to coat all sides evenly. Use an offset spatula to spread chocolate up the sides, creating a shell. Refrigerate for 5-10 minutes, until set but slightly tacky.
Step 6: Remove the mold from the refrigerator. Spoon the pistachio kadaif filling into the chocolate shells, gently pressing it down evenly. Leave a small gap at the top edge for the final chocolate layer.
Step 7: Re-temper your remaining chocolate if needed. Pour the remaining tempered chocolate over the filling, spreading to cover completely and smooth the surface. Lightly tap the mold on the counter to release air bubbles.
Step 8: Place the mold back into the refrigerator for at least 30-45 minutes, or until the chocolate bars are completely firm and easily release from the mold. Carefully demold and store in an airtight container at cool room temperature or in the refrigerator.