01 - Combine chopped dates with water in a small saucepan. Cook over medium heat for 5–7 minutes until dates soften and mixture thickens into a paste. Stir in orange blossom water and lemon juice. Cool completely.
02 - Whip chilled heavy cream in a mixing bowl until soft peaks form. Refrigerate until ready to use.
03 - Beat egg yolks with half the sugar and vanilla extract in a separate bowl until mixture becomes pale and thickened.
04 - Whisk egg whites with salt in a clean bowl until foamy. Gradually add remaining sugar while beating until stiff glossy peaks form.
05 - Gently fold cooled date paste into the egg yolk mixture until fully incorporated.
06 - Fold whipped cream into date-yolk base, then gently incorporate egg whites using a rubber spatula. Stop when mixture appears smooth and airy.
07 - Divide mousse among individual serving glasses. Refrigerate for at least 2 hours until completely set.
08 - Top each portion with chopped pistachios, orange zest, and dried rose petals if desired before serving.