Step 1: In a large skillet over medium heat, melt the butter and add the finely chopped kunafeh pastry. Fry for 5-8 minutes, stirring constantly, until it becomes a deep golden brown and very crispy. Set aside to cool completely.
Step 2: In a medium bowl, combine the cooled toasted kunafeh, pistachio cream, tahini, and a pinch of salt. Mix until the pastry is evenly coated.
Step 3: Melt two-thirds of your chocolate in a microwave or double boiler. If tempering, add the remaining third (the 'seed') and stir until smooth and slightly cooled.
Step 4: Pour a thin layer of chocolate into deep silicone bar molds. Tilt the molds to ensure the sides are coated. Place in the fridge for 5-10 minutes to set.
Step 5: Once the chocolate shell is firm, pack the pistachio-kunafeh mixture into the molds, leaving a small gap at the top. Pour the remaining melted chocolate over the filling to seal the bars. Scrape off any excess with a bench scraper.
Step 6: Chill the bars in the refrigerator for at least 30-60 minutes until completely set. Carefully unmold and serve at room temperature.