For the Marshmallow Layer, blend cream cheese, sugar, flour, and vanilla until smooth. Melt marshmallows with heavy cream, then add to the cream cheese mixture. Mix in egg, then spread over the baked crust evenly.
For the Chocolate Layer, blend cream cheese, sugar, flour, and cocoa powder until smooth. Melt chocolate chips with heavy cream, then add to the cream cheese mixture. Mix in egg, then spread over the marshmallow layer evenly.
Prepare a ganache topping by melting chocolate and heavy cream, pouring it over the cheesecake, top with marshmallows, browning them, and adding crushed graham crackers before serving.