- Crust: Preheat oven to 325F (160C). Stir crumbs with butter. Press over bottom of a 9-1/2-inch (24-cm) springform pan. Bake in centre of preheated oven for 8 to 10 minutes. Cool.
- Filling: Coarsely chop chocolate into small pieces. Melt in a small heavy-bottom saucepan set over low heat, removing from heat when some pieces of chocolate are still visible, about 5 minutes. Stir until smooth. Or microwave, uncovered, on medium power until chocolate is almost, but not completely, melted, from 3-1/2 to 4-1/2 minutes. Then stir.
- In a large mixing bowl, using an electric mixer, or in a food processor, beat or whirl cream cheese with coffee crystals and sugar until smooth, about 2 minutes. Stop and scrape sides of bowl often. Beat or whirl in eggs, 1 at a time. Beat or whirl in melted chocolate and vanilla.
- Turn filling onto warm crumb crust and smooth top. Bake in centre of preheated 325F (160C) oven until centre of cheesecake seems set when jiggled and a cake tester comes out almost clean, from 1 hour to 1 hour and 10 minutes. Cool 10 minutes on a wire rack. Then, to minimize cracking, run a sharp knife around edge of pan to loosen cake. Don't remove sides. Cool on a rack.
- Then cover with plastic wrap and refrigerate until cold, about 6 hours or up to 2 days. Cake freezes well. Serve with a dusting of icing sugar.
For a dense rich cake, whirl filling ingredients together in a food processor. An electric mixer gives a higher lighter cake.
Boxes of Oreo baking crumbs are sold in grocery stores. We preferred this cake made with regular cream cheese and bittersweet chocolate.