Melt 2 tablespoons unsalted butter in a large skillet over medium heat. Add 1 cup dried kataifi and cook, stirring occasionally, until golden-brown and crispy, 5 to 8 minutes. Transfer to a medium bowl.

Immediately stir in 3 tablespoons creamy pistachio butter, ¼ cup coarsely chopped roasted, salted pistachios, 1 tablespoon tahini, and ¼ teaspoon kosher salt until combined.

Heat ½ cup of the heavy cream in a microwave-safe bowl until hot to the touch, about 1 minute. Stir in 1 cup chocolate chips. Let sit for 5 minutes for the chocolate to melt. Whisk together until smooth. Let cool to room temperature, about 10 minutes.

Beat the remaining 1 cup plus 2 tablespoons cold heavy cream in a medium bowl with an electric hand mixer or with a whisk by hand until soft peaks form. Transfer ¾ cup to a small bowl and refrigerate for topping the finished mousses before serving.

Continue whipping the remaining whipped cream until stiff peaks form. Fold the whipped cream into the cooled chocolate mixture with a large flexible spatula in three additions.

Divide half the chocolate mixture between 6 (6 to 8-ounce) ramekins or glasses (about 3 scant tablespoons each). Reserve ¼ cup pistachio mixture for garnish, then divide the remaining between the glasses (about 2 tablespoons each). Top with the remaining chocolate mixture. Refrigerate at least 1 hour and up to 2 days.

Just before serving, top with the reserved whipped cream, reserved pistachio mixture, 2 tablespoons coarsely chopped pistachios, and a pinch of flaky salt.