Preheat the oven to 350 degrees F or 175 degrees C.
Grease a 3-inch by 9-inch springform pan with butter.
Blend cookies, coffee granules and sugar in a processor and add melted butter until the ingredients blend properly.
Spread the prepared mixture evenly onto bottom and not sides of prepared pan.
Bake for 5 minutes and set aside to cool. Maintain oven temperature.
Melt the chopped bittersweet chocolate over a double boiler and stir occasionally until the chocolate melts.
Cool the melted chocolate till it is lukewarm, but make sure it is still pourable.
Now, add cocoa powder, instant coffee granules, cornstarch and sugar in a processor and blend, until smooth.
Mix softened cream cheese and beat well till the cheese gets incorporated properly and all lumps disappear.
Stir in the 4 eggs to it, one at a time, mixing slowly after each just until blended. Add vanilla extract with the last egg.
Also add lukewarm chocolate and chopped pecans to this mixture and stir until it blends properly.
Pour filling over the prepared crust and smoothen the top surface.
Bake at 350 degrees F for 15 minutes, and then reduce the temperature to 200 degrees F and bake for another 2 hours.
Cool for 5 minutes. Run knife around the rim of pan to loosen cake and chill overnight.
Melt chocolate chips, sugar and milk in a saucepan over low heat, until smooth.
Pour marshmallow cream on the center of the cheesecake, and then spread it evenly over the top.
Drizzle a layer of the chocolate mixture on the marshmallow cream and garnish with bittersweet chocolate curls and chopped pecans.
Transfer cheesecake to platter and serve chilled!!