In a small pan, melt the butter over medium heat. Add in the kataifi and stir continuously until golden brown for about 5 minutes. Place toasted kataifi into a bowl along with pistachio cream and mix until combined.
In the loaf pan, drizzle the melted white chocolate in a zig zag pattern and refrigerate for 5 minutes. Next pour half of the melted dark chocolate into the loaf pan and spread evenly - refrigerate 10 minutes. Transfer the kataifi mixture to the pan and spread out evenly. Top with remaining dark chocolate and spread out evenly. Refrigerate for 3 hours or until set.