If frozen, thaw kunafa (kataifi) dough completely, then pull apart into very small, fine pieces.
In a large skillet over medium heat, melt unsalted butter or ghee, add shredded kunafa and cook, stirring constantly, until golden brown and crispy, about 8–10 minutes; transfer to a paper-towel–lined plate to cool.
In a medium bowl, combine cooled crispy kunafa with pistachio butter or pistachio cream and optional sea salt; mix until thick and cohesive.
Melt chopped good quality milk or dark chocolate in a double boiler or microwave in 30-second intervals, stirring until smooth.
Pour a thin layer of melted chocolate into a chocolate bar mold (or parchment-lined pan), brush up sides to form a shell, then chill in the refrigerator until firm, about 5–10 minutes.
Spoon the pistachio-kunafa filling evenly into the chilled chocolate shells, gently pressing to form a compact layer.
Cover the filling with remaining melted chocolate, tap out air bubbles, then chill until completely set, about 30–60 minutes; unmold or cut into bars and serve.