01 - Combine chopped dates and water in a small saucepan. Cook over low heat for 3-4 minutes, stirring constantly until soft and jammy. Remove from heat and let cool to room temperature.
02 - In a large chilled bowl, whip cold heavy cream using an electric mixer or whisk until soft peaks form. Refrigerate immediately to maintain structure.
03 - Whisk egg yolks with granulated sugar in a separate bowl until pale and thickened, approximately 2-3 minutes. Stir in orange blossom water and lemon zest until fully incorporated.
04 - Transfer cooled date mixture to a food processor or blender. Process until completely smooth, then fold into the egg yolk mixture until homogeneous.
05 - Gently fold refrigerated whipped cream into the date-yolk base in two additions. Use a spatula with light, lifting motions to maintain airiness and prevent deflation.
06 - In a clean, grease-free bowl, whisk egg whites to stiff peaks using a hand mixer or whisk. Carefully fold into the mousse base using gentle folding motions to preserve volume.
07 - Divide mousse evenly among individual serving glasses or bowls. Refrigerate for a minimum of 2 hours until completely set and firm.
08 - Just before serving, sprinkle chopped pistachios and finely grated orange zest over each portion. Add sliced dates if desired for additional texture and presentation.