01 - Toast pistachios in a small skillet over medium heat for 2–3 minutes. Add honey, stir to coat evenly, and cook for 1 minute more. Spread mixture on parchment paper and allow to cool completely.
02 - Place chopped chocolate and butter in a heatproof bowl set over a pan of simmering water (bain-marie). Stir continuously until completely melted and smooth. Remove from heat and let cool slightly.
03 - Whisk egg yolks, granulated sugar, ground cardamom, and salt into the warm chocolate mixture until glossy and well incorporated.
04 - In a chilled bowl, whip 0.5 cup heavy cream using a hand or stand mixer until soft peaks form.
05 - In a separate clean bowl, beat egg whites with electric mixer until stiff glossy peaks form.
06 - Gently fold whipped cream into the chocolate mixture until just combined. Then fold in beaten egg whites in two separate additions, being careful not to deflate the mixture.
07 - Divide half the chocolate mousse evenly among 4 serving cups or glasses. Sprinkle a layer of cooled pistachio crunch over each portion. Top with remaining mousse. Refrigerate for at least 2 hours until set.
08 - Whip 0.5 cup heavy cream with powdered sugar and rosewater until soft peaks form.
09 - Top each chilled chocolate cup with a generous spoonful of rosewater cream. Garnish with extra chopped pistachios and dried rose petals if desired. Serve immediately.