Prepare the Tart Crust: In a mixing bowl, whisk together the all-purpose flour, granulated sugar, and salt. Cut in the cold butter until the mixture resembles coarse crumbs. Gradually add the ice water, mixing just until the dough comes together. Shape the dough into a disk, wrap it, and refrigerate for at least 30 minutes.
Roll and Shape the Crust: Lightly flour your work surface and roll the chilled dough into a round large enough to fit a 9-inch tart pan. Carefully transfer the dough to the pan and gently press it into the bottom and sides. Trim away any excess dough and chill the crust while preparing the filling.
Prepare the Dark Chocolate: Place the chopped dark chocolate in a heatproof bowl. Warm the heavy cream until steaming but not boiling, then pour it over the chocolate. Let it sit for about 2 minutes, then stir until smooth and glossy. Allow the chocolate mixture to cool slightly.
Make the Pumpkin Filling: In a separate bowl, whisk together the pumpkin puree, brown sugar, eggs, vanilla extract, cinnamon, ginger, nutmeg, cloves, and salt until smooth. Slowly whisk in the slightly cooled chocolate mixture until everything is fully combined and silky.
Fill the Tart Shell: Remove the chilled crust from the refrigerator and pour the chocolate pumpkin filling into the prepared tart shell. Smooth the surface gently with a spatula and lightly tap the pan against the counter to release any large air bubbles.
Bake the Tart; Preheat the oven to 350°F (175°C). Place the tart pan on a baking sheet and bake for 40–45 minutes, or until the edges are set while the center still has a slight jiggle. Avoid overbaking because the filling will continue to set as it cools.
Cool and Chill; Transfer the baked tart to a wire rack and allow it to cool completely at room temperature. Once cooled, refrigerate for at least 2 hours so the filling can fully set and become easy to slice.
Garnish and Serve: Top the chilled tart with whipped cream, dark chocolate shavings, and optional toasted pecans. Slice with a sharp knife and serve chilled or slightly cool.