For the Crust
Place rack into the center of oven and preheat to 350 degrees F. Combine graham cracker crumbs from food processor and sugar in a medium bowl. Add butter and stir until evenly distributed. Press graham cracker/butter mixture into the bottom and 2 to 3 inches up the sides of a 9-inch nonstick springform pan. Bake 12 minutes or until lightly browned. Remove from oven and set aside to cool.
For the Filling
Using a double boiler, melt the chocolate until smooth. Cool chocolate until lukewarm, stirring occasionally.
In a food processor, combine cream cheese, sugar and salt until evenly mixed. With processor running, add whipping cream and process until evenly blended. Add melted chocolate. Add eggs 1 at a time completely blending between each egg. Continue blending until smooth. Pour filling into crust.
Bake cheesecake 50 to 60 minutes or until the outer edges start to puff and the cheesecake is set in the center. Remove cheesecake from oven and refrigerate 8 hours to overnight.
For the Topping
In a large metal bowl, whisk together sugar, egg whites, water, cream of tarter, and salt. Place bowl over a pan of simmering water (double boiler), and whisk continually until sugar is completely dissolved and mixture thickens, 2 to 3 minutes. When the mixture is hot to the touch remove from over water. Stir in marshmallows and allow to soften, about 3 minutes. Return bowl to over simmering water and using an electric hand mixer beat to stiff peaks, 3 to 4 minutes. Add vanilla and mix well.
Scrape topping onto chilled cheesecake and spread evenly to edges. Let stand 15 minutes.
Using a kitchen torch, lightly brown the topping peaks. Chill until completely cold.
To add a summer twist, mix chopped berries in medium bowl and use to garnish.