Melt white chocolate in a double boiler or microwave in 30-second intervals, stirring between each.
Stir in pistachio nut butter until smooth and thick.
Add Rice Krispies and toasted kataifi pastry, mixing until completely coated.
Line an 8x8 inch pan with parchment paper.
Press mixture firmly into pan to pack down evenly.
Cool at room temperature for 30 minutes or refrigerate for 15 minutes.
Melt dark and milk chocolates together using double boiler or microwave.
Pour melted chocolate over cooled base and spread evenly.
Sprinkle chopped pistachios and sea salt flakes over wet chocolate.
Let chocolate set completely, about 20 minutes at room temperature or 10 minutes in fridge.
Cut into 12 squares with a sharp knife, cleaning blade between cuts.