If you like truffles, this is the tart for you. As part of the Dessert Project, we made 3-inch tartlets with two different crusts (almond and chocolate), but this recipe also makes a 9-inch tart; recipes for the pre-baked tart shells are here. Techniques in this recipe: pre-baking tart shells, working with chocolate.

Filling

1 cup heavy cream
1 T cognac
12 oz (340 g) bittersweet chocolate, chopped fine
6 T unsalted butter, cut into thin slices and softened

Bring the cream to a brief simmer in a small saucepan over medium-high heat. Off heat, stir in chocolate and butter. Cover the pan and let stand until the chocolate is mostly melted, about 2 minutes. Gently stir the mixture until smooth, then stir in the cognac.

Pour the mixture into the pre-baked tart shell(s) and refrigerate, uncovered, until the filling is firm, about 2 hours.

Notes: Use good-quality dark chocolate containing a cacao percentage between 60% and 65%, for example, Callebaut Intense Dark Chocolate, L-60-40NV, or Ghirardelli 60% Cacao Bittersweet Chocolate.
For Espresso Truffle Tart, omit cognac and add 2 t instant espresso powder to the hot cream with chocolate.
For Peanut Butter Truffle Tart, spread ½ cup smooth peanut butter over the bottom of the tart shell and refrigerate while preparing the chocolate filling. Smooth chocolate over the peanut butter and chill as directed.

Source: Cook’s Illustrated Cooking School