Prep Your Liners: Line a muffin tin with 12 cupcake liners. Set aside.
Melt the Chocolate: In a heatproof bowl, melt the chocolate (with oil if using) using a double boiler or microwave in 30-second intervals. Stir until smooth.
Make the Chocolate Shell Base: Spoon 1–2 teaspoons of melted chocolate into each cupcake liner. Use the back of a spoon or pastry brush to coat the base and about halfway up the sides. Chill in the freezer for 5–10 minutes to set.
Mix the Filling: In a bowl, gently mix your pre-toasted kataifi with the pistachio cream and tahini until it becomes a thick, spoonable mixture. It should be rich but still have crunch.
Assemble the Cups: Remove the chilled chocolate cups. Add a generous spoonful of filling into each one, pressing lightly to flatten but not overflow.
Seal the Tops: Spoon more melted chocolate over the top of each filled cup, spreading to the edges to seal. Tap the pan gently to level.
Decorate (Optional): While the top is still soft, sprinkle with toppings like chopped pistachios or extra kataifi.
Chill Until Set: Refrigerate for 1 hour or until firm. Peel off liners and serve cold or slightly softened at room temp.