Preheat oven to 375 degrees F.
Roll the dough out on a lightly floured surface to a 12-inch circle. Carefully transfer the dough to a 10-inch fluted tart shell with removable bottom and ease the pastry into the bottom and sides of the shell. Press the dough into the shell and trim the top edges to form a clean edge. Using the tines of a fork, lightly dock the base of the shell. Place the shell into the oven and bake until lightly browned, 12 to 15 minutes. Remove from the oven, brush the baked shelled bottom with the egg white, and sprinkle with the chopped pecans. Set aside until ready to use.
Rub the sweet potatoes with the vegetable oil and roast in the oven for 45 to 60 minutes, until very tender. Remove and set aside to cool. Peel the potatoes and pass the flesh through a fine mesh sieve using a rubber spatula. You should have about 1 1/2 cups smooth sweet potato puree.
In a medium mixing bowl, combine the sweet potato puree with the sugar, maple syrup, ginger, cinnamon, nutmeg, cloves and salt. Whisk to combine. In a separate bowl, combine the heavy cream with the eggs and whisk to combine. Add the cream and egg mixture to the sweet potato mixture and stir to blend. Pour the batter into the prepared tart shell and place the tart on a sheet pan. Bake until the center is set and the tart is golden brown, about 30 to 35 minutes. Remove the tart from the oven and allow to cool for at least 20 minutes before serving.
To serve, slice the tart into 8 servings. Spoon 3 to 4 tablespoons of the anglaise onto each dessert plate, then top with a slice of the tart. Drizzle each slice with some of the chocolate sauce and dust with powdered sugar. Serve immediately.
Sift the flour, sugar and salt into a large bowl. Add the butter. Using your fingers, 2 knives, or a pastry blender, work the butter into the dry ingredients until the mixture resembles coarse crumbs. Add the water, 1 tablespoon at a time, until the dough just comes together, being careful not to over mix. (You may not need all of the water.)
Form the dough into a smooth ball, flatten into a disk, and wrap in plastic wrap. Refrigerate for at least 30 minutes, and up to 2 days.
Yield: enough dough for a 10-inch tart
Heat the heavy cream, milk and vanilla bean in a large, heavy-bottomed saucepan over medium heat. Place the egg yolks and sugar in a heatproof mixing bowl and beat until pale yellow in color and all of the sugar has dissolved. Ladle about 1/2 cup of the hot cream mixture into the egg mixture and whisk vigorously to combine. Add the egg mixture to the hot cream mixture in the saucepan and cook, stirring constantly with a whisk or wooden spoon. Be sure to stir in the corners of the pot and lower the heat slightly. Stir the mixture until the custard has thickened enough to coat the back of a spoon, 4 to 5 minutes. Remove from the heat and strain the custard through a fine mesh sieve into a clean bowl. Place the bowl in another bowl half-filled with ice and water and stir occasionally until chilled.
Yield: 2 1/2 cups
In a small, heavy saucepan, bring the cream to a bare simmer over low heat. Place the chocolate pieces in a medium bowl. Pour the cream over the chocolate and let sit for 2 minutes. Whisk in the vanilla and continue whisking until the sauce is smooth and thick. Let the sauce cool to room temperature before serving.
Yield: 3/4 cup