Step 1: Prepare Your Kataifi. Preheat your oven to 350°F (175°C). Spread the kataifi evenly on a baking sheet. Drizzle with a tablespoon of melted butter or neutral oil. Bake for 10-15 minutes, tossing halfway through, until golden brown and crispy. Keep a close eye on it as it can burn quickly. Once done, remove from oven and let cool completely.
Step 2: Prepare Your Pistachios. If using raw pistachios, spread them on a separate baking sheet and toast in the same oven for 5-7 minutes, until fragrant. If using roasted, simply chop them roughly.
Step 3: Melt the Filling Chocolate. In a heatproof bowl set over a saucepan of simmering water (bain-marie) or using a microwave in 30-second intervals, melt 100g (about 3.5 oz) of milk chocolate chips or chopped milk chocolate until smooth.
Step 4: Create the Filling. In a large bowl, combine the cooled crispy kataifi, chopped pistachios, and the melted milk chocolate. Add the tahini and gently fold everything together until well combined. The mixture should be sticky but still have distinct pieces of kataifi and pistachio.
Step 5: Prepare Your Mold. Line an 8x4 inch (or similar size) loaf pan or a specific chocolate bar mold with parchment paper, leaving an overhang on the sides to help lift the finished bar out easily.
Step 6: Melt the Base Chocolate. Melt the remaining 250g (about 8.8 oz) of milk chocolate using the same bain-marie or microwave method until completely smooth and glossy.
Step 7: Build the Base Layer. Pour about two-thirds of the melted milk chocolate into the prepared mold. Use an offset spatula or the back of a spoon to spread it evenly across the bottom and slightly up the sides, creating a shell. Place in the refrigerator for 5-10 minutes to set, until just firm but not completely hard.
Step 8: Add the Filling. Spoon the kataifi-pistachio filling evenly over the set chocolate base. Gently press it down with the back of a spoon or your fingers to create a compact, even layer.
Step 9: Top with Remaining Chocolate. Pour the remaining melted milk chocolate over the filling, spreading it carefully to cover the entire surface. Tap the mold gently on the counter a few times to release any air bubbles and ensure an even top.
Step 10: Chill to Perfection. Place the chocolate bar in the refrigerator for at least 2-3 hours, or until completely firm.
Step 11: Slice and Serve. Once fully set, use the parchment paper overhang to lift the bar out of the mold. Place it on a cutting board and, using a sharp knife, carefully slice it into individual bars. Warm the knife under hot water and wipe it dry for cleaner cuts if desired. Enjoy!