Preheat oven to 300 degrees. Spray mini cheesecake pan with nonstick baking spray.
Combine graham cracker crumbs, sugar and melted butter in small bowl. Divide evenly in pan and press down to create the crust.
In stand mixer blend cream cheese and, sugar until creamy and fluffy. Add the egg and vanilla; mix just until blended in. Stir in 1/2 cup of chocolate chips Divide evenly in the cheesecake pan over the crust.
Bake for 20-25 minutes or just until set. Remove from oven and turn oven off. Place marshmallows on the top of each cheesecake and place back in turned off oven for 2-3 minutes. Just enough to melt the marshmallows slightly together. Do not go longer than 3 minutes.
Refrigerate cakes for 2 hours to up to overnight. Remove from pan.
Melt remaining 1/2 cup chocolate chips according to manufacturers instructions on packaging. Drizzle over well chilled cakes.