Chocolate Truffle Tart

Preparation

1. Make crust:

   Step 1

   Put oven rack in middle position and preheat oven to 350°F. Wrap a sheet of foil over bottom of springform pan (in case of leaks). Lightly butter side of pan.

   Step 2

   Stir together ground wafers and butter in a bowl until combined, then pat mixture evenly onto bottom of pan and 1 1/2 inches up side. Bake until crust is slightly puffed, about 10 minutes, then cool completely in pan on a rack, about 15 minutes. Leave oven on.

2. Make filling while crust cools:

   Step 3

   Melt chocolate and butter in a 2-quart heavy saucepan over low heat, stirring until smooth, then remove from heat and cool 5 minutes.

   Step 4

   Whisk together eggs, cream, sugar, salt, and vanilla in a bowl. Whisk chocolate mixture into egg mixture until combined well.

3. Assemble and bake tart:

   Step 5

   Pour filling into cooled crust and rap pan once on counter to eliminate any air bubbles. Bake until filling 1 inch from edge is set and slightly puffed but center trembles slightly when pan is gently shaken, 20 to 25 minutes. (Center will continue to set as it cools.)

   Step 6

   Cool tart completely in pan on a rack, about 2 hours. Chill, uncovered, until center is firm, about 4 hours. Remove side of pan and sprinkle with cocoa to serve.