Prepare the Chocolate Shell:
Melt the white chocolate (if using) and drizzle into chocolate molds for decoration.
Melt the dark chocolate chips with 1 tablespoon of coconut oil.
Add about 2 tablespoons of melted chocolate into each mold, coating the bottom and sides.
Refrigerate molds to set the chocolate.
Make the Pistachio Filling:
Sauté the chopped kataifi in a pan with the remaining coconut oil until golden brown.
Remove from heat and mix in the pistachio butter and tahini until well combined.
Assemble the Bars:
Distribute the pistachio filling evenly into the chocolate-coated molds.
Top with more melted chocolate to seal.
Refrigerate until fully set.