Preheat oven to 350°F/171°C. Grease and line two 8-inch square pans. Set aside.
Prepare crust: Combine graham crumbs, melted butter and white sugar in a bowl until all crumbs are coated with butter. Lightly press the crumb mixture into prepared pans.
Prebake the crust for about 8-12 minutes. Remove from the oven and let it cool.
In a bowl, mix together brownie ingredients until smooth. Evenly divide among the pans and pour this over the cooled prebaked crusts.
In another mixer bowl, cream together cream cheese and sugar. Add in egg and vanilla extract.
Dollop cheesecake topping into brownies. Run the mixture with a knife or a skewer stick to make a swirl.
Bake the brownies for around 20-25 minutes. Until the cheesecake is set.
Once baked, top with the marshmallows, broil or torch the mallows until melted and slightly browned.