This rich, creamy (and surprisingly easy!) chocolate tart is the most-requested recipe at the Savory Spoon Cooking School in Door County, Wisconsin.
Preheat oven to 400°F.
For the pastry dough, in a medium bowl stir together melted butter, the 1/4 cup sugar, vanilla paste and salt. Stir in flour. (The dough will seem a bit oily.) Press the pastry mixture evenly into a 9-inch fluted tart pan with a removable bottom. (Pat the mixture into the sides first—don't skimp, they need to be sturdy—then fill in the bottom crust.) Place the tart pan on a baking sheet. Bake 14 to 16 minutes or until golden, covering edges with foil if needed to prevent over-browning. Transfer to a cooling rack while still on the baking sheet; leave oven on.
Meanwhile, for the filling, in a medium saucepan bring half-and-half and sugar to a simmer over medium-low heat, stirring occasionally. Simmer, stirring constantly, for 3 minutes. Remove from heat. Add chopped chocolate, stirring constantly, until chocolate is melted and mixture is smooth. (It will look curdled at first but should become smooth and glossy as the chocolate melts; if flecks remain after stirring, return pan to low heat for a moment to finish melting.)
In a medium bowl, whisk egg until foamy. Whisk 2 tablespoons of the warm (not hot) chocolate mixture into the egg. Drizzling slowly, whisk in the remaining chocolate mixture.
Immediately pour filling into the warm crust. Return baking sheet with tart to the oven, then turn the oven off. Let the tart sit in the hot oven until filling sets around edges but center 4 inches jiggle when gently shaken, 12 to 13 minutes.
Transfer to a wire rack. Cool completely, about 1 hour, before removing from the pan to slice. If desired, serve with sweetened whipped cream or fruit, such as berries. Or, cover and refrigerate tart for up to 2 days. (Bring tart to room temperature for about 20 minutes before serving, so that it's not too firm. It won't be quite as pretty and shiny but will taste as good.)
*Look for 60- to 70-percent cacao bittersweet chocolate. You can use chocolate disks or morsels instead of chopping chocolate bars.