Step 1: Preheat your oven to 350°F (175°C) and grease a 9-inch tart pan with a removable bottom.
Step 2: In a medium bowl, combine the chocolate wafer crumbs and melted butter, mixing until it resembles wet sand. Press the mixture firmly into the bottom and sides of the tart pan.
Step 3: Bake the crust for 10-12 minutes until set, then remove from the oven and let it cool completely on a wire rack.
Step 4: In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer. Do not let it boil.
Step 5: Place the chopped dark chocolate in a heat-proof bowl and pour the hot cream over it. Let it sit for 2 minutes, then stir gently until smooth and glossy.
Step 6: Whisk in the pumpkin puree, pumpkin pie spice, vanilla extract, and salt until the mixture is fully incorporated and uniform in color.
Step 7: Pour the filling into the cooled crust and smooth the top with a spatula. Refrigerate for at least 4 hours, or preferably overnight, before serving.