In a small microwave-safe bowl, melt ¼ cup white chocolate chips at 30-second intervals, stirring between each one. Once melted, stir in 3 drops oil-based green food coloring until you have a smooth, even color.
Using a spoon or fork, drizzle the green chocolate into the bottom of each of the four cavities of the mold. Place the mold in the refrigerator for 5 to 10 minutes for the drizzle to set.
Melt 2 cups dark chocolate chips in a medium bowl in the microwave at 30-second intervals, stirring between each one until smooth.
Remove the mold from the fridge and pour about two-thirds of the melted dark chocolate into the cavities, dividing it evenly.
Use the back of a spoon or a pastry brush to spread the chocolate, making sure the bottom and all sides of each cavity are completely and thickly coated. Shake off any excess chocolate and use the back of a knife to run around the flat top of the mold to remove any excess chocolate. Place in the refrigerator for 10 to 15 minutes until the shells are firm.
Meanwhile, use your hands to crush up 6 ounces kataifi dough in a large bowl and set aside.
Melt 4 tablespoons salted butter in a large skillet over medium-low heat. Add the kataifi6 ounces kataifi dough and toast it, stirring constantly, for 8 to 10 minutes until it is deep golden brown and crispy. Transfer to a plate to cool completely.
In a large bowl, stir 12 ounces pistachio cream, ⅓ cup tahini, and ¼ teaspoon salt until well combined.
Fold in the cooled kataifi until it is evenly distributed.
Spoon the pistachio filling into the chilled chocolate shells. Gently press the filling down with your hands to fill the bars and level them, leaving a small gap at the top for the final chocolate layer.
Reheat the remaining chocolate, if needed, and pour it over the filling to seal the bars.
Place the mold back in the refrigerator and chill for at least 1 hour, or until it is completely solid.
Once fully set, carefully turn the mold over and flex it gently to release your finished bars.