01 - Combine chopped dates with water in a small saucepan. Cook over medium heat for 5-7 minutes until dates soften and mixture forms a thick paste. Stir in orange blossom water and lemon juice. Cool completely before proceeding.
02 - Whip chilled heavy cream in a mixing bowl until soft peaks form. Refrigerate immediately 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 a pinch of salt in a clean bowl until foamy. Gradually add remaining sugar while beating until stiff peaks form.
05 - Gently fold cooled date paste into the egg yolk mixture until fully incorporated and uniform.
06 - Fold whipped cream into the date-yolk mixture. Gently incorporate beaten egg whites until mousse is smooth and airy, taking care not to deflate the mixture.
07 - Spoon mousse into individual serving glasses. Refrigerate for at least 2 hours until completely set.
08 - Top each serving with chopped pistachios, orange zest, and dried rose petals if desired. Serve chilled.