To make the crust, add the flour, sugar, lemon zest and salt to the bowl of a food processor. Pulse to combine. Add the cubed butter to the flour mixture and pulse a few times, until just combined and the mixture resembles a coarse meal. Add the ice-cold milk and mix briefly, about 5 seconds, or until a soft dough starts to form. Transfer the dough on a floured working surface and shape it into a thick disk. Dust with flour on top and set aside.
Preheat the oven to 375°F (180°C) and set an oven rack in the middle position.
Roll the dough to a thin round, approximately 13 inches (32 cm). Lay the dough loosely into a 9½-inch (24-cm) fluted tart pan with a removable bottom. Press firmly against the pan so the finished edge is slightly higher than the pan. Trim the excess using a knife and freeze for 10 to 15 minutes.
Place pie weights (or dried beans) on top of the Short Crust to prevent it from rising. Bake the short crust for 20 minutes, or until the edges start to brown slightly. Leave the crust in the pan to cool completely.
To make the filling, add the milk to a saucepan and reserve 3 tablespoons (45 ml) of it in a cup. Add the cooking cream, sugar and salt to the saucepan and bring to a boil over medium heat. Mix the reserved milk with the cornstarch until well dissolved.
Add the cornstarch mixture to the boiling milk and cream, and cook on low for 7 to 8 minutes, stirring continuously so it doesn’t stick to the pan, until thickened. Add the pumpkin puree, cinnamon, ginger, cloves and nutmeg and cook for another minute. Remove the pan from the heat and add the maple syrup and whiskey. Mix until well combined. Pour the hot filling into the pre-baked short crust and let cool completely at room temperature, then refrigerate for at least 4 hours or overnight.
When ready to serve, prepare the garnishes. In a small bowl with a pouring spout, mix the maple syrup and bourbon whiskey. Set aside.
Blot the top of the Pumpkin Filling dry with paper towels. Sprinkle the caster/superfine sugar all around the surface, then, using a butane torch, heat the sugar until melted and caramelized.
Slice the pumpkin tart and plate on serving plates: add a dollop of whipped cream on the side of each slice, and top with the maple and bourbon syrup. Sprinkle with a dash of ground nutmeg and enjoy! Keep the pumpkin tart refrigerated, for up to 5 days, in an airtight container.