Melt the butter in a large skillet over medium heat. Add the short kataifi strands and cook, stirring frequently, for 8–12 minutes until evenly golden and crisp. Reduce heat if patches brown too quickly. Transfer to a bowl and cool for about 10 minutes.

Stir the pistachio cream, tahini and salt together, then fold in the cooled toasted kataifi. Keep the strands textured rather than blending them.

Put the chocolate in a completely dry microwave-safe bowl. Heat in 20-second bursts at medium power, stirring after each, until just melted and smooth. Avoid overheating or adding water. This recipe uses refrigeration to set the chocolate.

Use about two thirds of the chocolate to coat the bottoms and sides of the two molds, sharing it evenly. Set the molds on a tray and refrigerate for 10–15 minutes until the shells are firm.

Divide the filling between the shells, pressing gently into the corners without breaking the shell. Keep the filling below the rim so the chocolate cap can seal to the sides.

Gently rewarm the reserved chocolate if needed, then spread it over the filling to seal each bar. Refrigerate for 25–30 minutes or until completely firm. Unmold carefully.

Cut each bar into 8 pieces with a clean knife. Serve 2 pieces per portion. Keep covered in the refrigerator and bring out only the amount needed; the shell softens as it warms.