Crust:
Preheat oven to 350°F (180°C).

Grease a 10 inch (25 cm) springform pan. Line base and side with parchment paper.

Combine cookie crumbs, sugar and butter in a medium bowl. Using a flat-bottomed glass, press mixture over base of prepared pan.

Place on a baking sheet. Bake in preheated oven for 15 minutes; cool.

Filling:
Reduce oven temperature to 325°F (160°C).

Place chocolate in a small saucepan. Stir over low heat until chocolate is almost melted. Remove from heat and stir until melted; cool slightly.

Beat remaining ingredients in a large bowl with electric mixer until smooth. Add chocolate and beat until combined.

Pour mixture onto prepared crust.

Bake in preheated oven for about 1 hour or until filling is set. Refrigerate, covered, for 8 hours or overnight.

Whip extra cream and spoon over each slice.