In a medium saucepan, heat the heavy cream over medium heat until it just begins to simmer. Remove from heat and add the semi-sweet chocolate chips. Let sit for 2-3 minutes to melt the chocolate, then whisk until smooth and fully combined. Stir in the vanilla extract.

Allow the chocolate mixture to cool to room temperature. Once cooled, use an electric mixer to whip the mixture until it thickens and forms soft peaks, about 3-4 minutes.

In a separate bowl, gently mash half of the fresh raspberries with the powdered sugar until you achieve a chunky sauce. Fold the raspberry mixture into the chocolate mousse until well combined.

Spoon the mousse into individual serving cups, filling them about three-quarters full. Top with the remaining whole raspberries and a sprinkle of crushed graham crackers if desired.

Refrigerate the mousse cups for at least 2 hours to set. Serve chilled, garnished with fresh mint leaves if desired.