Preheat oven to 350 degrees F.

Crush the chocolate graham crackers in a food processor until fine and uniform, resembling coarse sand with no chunks remaining. Transfer crumbs to a large mixing bowl.

Melt the butter and pour it over the crumbs. Stir until every crumb is coated and no dry spots remain. The mixture should hold its shape when pressed between your fingers.

Press the crust firmly and evenly into the bottom and up the sides of the tart pan. No need to grease it. Bake for 7 to 9 minutes until just set. Remove from oven and allow to cool completely before adding any filling.

Combine the fresh raspberries, sugar, and lemon juice in a saucepan over medium heat. Gently crush the berries with a wooden spoon as they warm. Bring to a low boil, about 5 minutes, then remove from heat.

Blend the coulis with an immersion blender until smooth. Pour through a fine mesh sieve, pressing gently to remove all seeds. Set the strained coulis aside to cool completely before using.

Place the finely chopped bittersweet chocolate and heavy cream together in a microwave-safe bowl. Heat in 15-second increments, stirring well after each burst, until fully melted and smooth. Do not overheat. Stir in the vanilla extract and salt.

Pour 1 cup of the cooled raspberry coulis into the bottom of the cooled crust and spread evenly to coat the entire surface. Reserve the remaining coulis for drizzling at serving.

Spoon the warm chocolate ganache filling evenly over the raspberry layer. Use a rubber spatula to spread gently to the edges without disturbing the coulis beneath.

Refrigerate for at least 2 hours or preferably overnight until the ganache is completely set and firm. Top with fresh raspberries and a drizzle of reserved coulis just before serving.