In a mixing bowl, combine graham cracker crumbs, melted butter, and sugar. Stir until the crumbs are evenly coated with butter. Distribute into small cups, pressing down firmly to form a compact crust. Set aside.

In a large bowl, beat softened cream cheese with powdered sugar, vanilla extract, lemon zest, and fresh lemon juice using an electric mixer on medium speed for 2-3 minutes until smooth and creamy.

In a chilled bowl, whip heavy whipping cream until stiff peaks form, taking about 3-5 minutes on medium-high speed.

Gently fold whipped cream into the cream cheese mixture in batches, combining slowly with a spatula to maintain airiness.

Using a spoon or piping bag, fill each cup with the mousse mixture and smooth the tops with a spatula.

Cover each cup and refrigerate for at least 2 hours to allow the mousse to set properly.

Before serving, garnish with whipped cream, fresh lemon zest, or a lemon slice and a sprinkle of crushed graham crackers.