Roughly chop the kataifi pastry and place it in a skillet or pot with the butter. Cook over medium heat, stirring frequently, until the kataifi is golden, toasted, and crisp, about 8 minutes. Remove from heat, add the hazelnut or pistachio cream, and toss until the kataifi is fully coated. Set aside.

Melt the white chocolate in a heatproof bowl using either a bain marie (double boiler) or a microwave in 20-second intervals, stirring between each until most of the chocolate has melted. The residual heat will melt the remaining small pieces. Avoid overheating to prevent burning.

Melt the milk chocolate in the same manner.

Drizzle some melted white chocolate into the molds. Then, pour the milk chocolate and tilt the molds to cover them completely. Freeze the molds for 10 minutes, allowing the chocolate to harden.

Once set, fill the center of each mold with the kataifi mixture. Top off with more milk chocolate to seal the filling. Return the molds to the freezer to chill for about 15 minutes.

Once the chocolates are fully set, carefully remove them from the molds and trim off any excess chocolate. Serve and enjoy!