Melt the butter in a large skillet over very low heat.
Stir in the kataifi and continue to cook (stirring constantly) until toasty and fragrant (approx. 5 to 10 minutes).*
Mix in the pistachio cream, sesame oil (or tahini), salt, and food coloring (if using), until blended.
Melt the chocolate in 30-second intervals in the microwave, stirring until smooth.**
Place about 1 tablespoon of melted chocolate in the bottoms of each of 24 grease-proof cupcake liners, spreading it into an even layer and slightly up the sides. Spoon about 1 1/2 tablespoons of the kataifi filling over the chocolate, tapping it lightly to flatten.
Place about 2 tablespoons of melted chocolate over the filling, spreading/tapping/swirling the cup to remove any air bubbles and level the chocolate.
Garnish with chopped pistachios and flaky sea salt, if desired.
Set aside and allow the chocolate to harden before serving.