Cost per Serving:
Position a rack in middle of oven and preheat to 350°F
Make crust: Pulse cookies in a food processor until ground; set aside 1/4 cup. Add butter and sugar; pulse to combine. Press mixture evenly into a 10-inch tart pan with a removable bottom. Bake until dry and set, 8 minutes. Cool in pan on a wire rack. Mix remaining crumbs and cocoa in a bowl; set aside.
Make filling: Heat chocolate, cream, butter and salt in a bowl set over a pan of nearly simmering water; whisk until smooth. Remove bowl; whisk in eggs, sugar and vanilla. Put crust on a baking sheet; pour in filling.
Bake until filling is set around edges but slightly jiggly in center, 25 to 30 minutes. Cool on a wire rack for at least 1 1/2 hours.
Dust with crumb mixture; serve at room temperature.