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 cool to room temperature.
02 - Whip cold heavy cream in a large bowl until soft peaks form. Refrigerate immediately to maintain structure.
03 - Whisk egg yolks with granulated sugar in a separate bowl until pale and thickened. Stir in orange blossom water and lemon zest until fully incorporated.
04 - Process cooled date mixture in a food processor or blender until smooth paste forms. Fold into egg yolk mixture until uniform in color and texture.
05 - Gently fold whipped cream into date-yolk base in two additions, using a spatula with lifting motion to maintain airy texture.
06 - Whisk egg whites in a clean bowl until stiff peaks form. Carefully fold into mousse base, preserving maximum air volume for light texture.
07 - Distribute mousse evenly into individual serving glasses or bowls using a spoon or piping bag.
08 - Refrigerate for minimum 2 hours until mousse holds shape firmly when touched.
09 - Top each portion with chopped pistachios, grated orange zest, and sliced dates if desired. Serve chilled.