In a small saucepan, combine raspberries, sugar, lemon juice, and vanilla extract. Cook over medium heat for about 5 minutes, stirring occasionally, until the raspberries break down and the mixture thickens. Remove from heat and let it cool.

In a mixing bowl, combine graham cracker crumbs, melted butter, and salt. Press the mixture into the bottom of individual serving cups or a small cake pan to form the crust.

In a separate bowl, whip the heavy cream until soft peaks form. Gently fold in the mascarpone cheese until fully combined. Then, fold in the cooled raspberry mixture until just combined.

Spoon the raspberry mousse over the crust in the serving cups or pan. Sprinkle the crushed pistachios on top. Refrigerate for at least 2 hours to set.

Serve chilled and enjoy!