• Step 1: Preheat your oven to 375°F (190°C). In a food processor, combine the flour, chilled butter, sugar, and salt. Pulse until the mixture resembles coarse crumbs. Add a tablespoon of ice water and pulse again until the dough just begins to come together.
• Step 2: Transfer the dough to a lightly floured surface and gently knead it into a smooth disc. Press the dough into a 9-inch tart pan with a removable bottom, making sure to evenly cover the bottom and sides. Prick the bottom with a fork and bake for 20-25 minutes, or until the crust is golden brown. Allow the crust to cool completely on a wire rack.
• Step 3: In a medium saucepan, heat the heavy cream over medium heat, stirring occasionally, until it just begins to simmer. Remove the pan from the heat and add the chopped chocolate. Let the mixture sit for 2-3 minutes, then whisk until the chocolate is completely melted and the ganache is smooth. Stir in the vanilla extract.
• Step 4: Pour the chocolate ganache into the cooled tart crust, smoothing the top with a spatula. Refrigerate the tart for at least 2 hours, or until the ganache is set.
• Step 5: When ready to serve, remove the tart from the refrigerator and let it sit at room temperature for 5-10 minutes. Gently remove the outer ring of the tart pan and serve the Chocolate Ganache Tart chilled or at room temperature, garnished with a dusting of cocoa powder or a sprinkle of chopped nuts, if desired.