"I feel the end approaching.
Quick, bring me my dessert, coffee and liqueur."
- Pierette, great-aunt of Anthelme Brillat-Savarin

For the crust: Preheat oven to 400 degrees F. Grin the chocolate cookies in food processor until fine. Transfer to a bowl and work in the melted butter with your fingers until it is incorporated. Turn the crumbs into a 10-inch springform pan. Firmly and evenly press the crumbs into the bottom and
1 1/2 inches up sides of the pan. Freeze the crumb crust 10 minutes. Bake the frozen shell about 8 minutes until set, but soft when pressed gently on the bottom. Let cool on a rack.
For the ganache: In a small saucepan melt half of chopped chocolate in heavy cream over moderately low heat, stirring constantly. Remove from heat and stir in remaining chocolate until smooth. Let cool completely,
then stir in vanilla. Pour cooled ganache into the cookie crust and
refrigerate until set, at least 1 hour.
For the mousse: Pour 2 tablespoons water into a small bowl. Sprinkle gelatin over water and set aside to soften. In a medium saucepan combine milk with 1/2 cup sugar and cinnamon sticks. Scrape seeds from vanilla
bean into milk and add the bean as well. Bring to a boil over moderate heat. Lower heat and simmer gently 10 minutes. Meanwhile using electric mixer
at medium speed, beat egg yolks with whole egg and the remaining 1/2 cup sugar until thickened and light in color, about 2 minutes. Whisk the espresso powder into hot milk mixture until blended. Using a rubber spatula gradually stir hot espresso mixture into beaten eggs. Return mixture to saucepan and cook over moderate heat, stirring constantly, until custard coats back of spoon and reaches 170 degrees F. on an instant thermometer. Do not let boil. Remove from heat and strain the custard into a large bowl. Stir in the softened gelatin until blended. Place the bowl in a larger bowl filled with
ice water and stir custard frequently until chilled, 10 to 12 minutes.
In a separate bowl, beat heavy cream until stiff. Using a rubber spatula
fold whipped cream into custard in 2 additions. Scrape the mousse into cookie crust. Cover, lightly pressing wax paper onto surface of mousse
and refrigerate for at least 6 hours or overnight. Shortly before serving unmold the cake. With a thin sharp knife, cut around the sides of the cake
to loosen crust from pan. Release springform latch and remove the pan
side. Place cake on cake stand.
For the topping: In a large bowl beat heavy cream with confectioner's
sugar until nearly stiff. At low speed beat in coffee liqueur. Spoon cream onto the cake and spread it in waves with a rubber spatula. Dust with cinnamon just before serving.