S'mores Cheesecake

Chocolate Cheesecake:
2 oz. semi-sweet baking chocolate, coarsely chopped
¼ c. heavy whipping cream
3 (8 oz.) pkg. cream cheese, at room temperature
1 c. white sugar
⅓ c. unsweetened cocoa powder
⅛ c. homemade vanilla extract, or 2 tsp. store-bought vanilla extract
4 eggs, at room temperature

2 c. graham cracker crumbs
6 Tbsp. butter, melted

Marshmallow Topping:
8 large egg whites 
2 c. white sugar 
½ tsp. cream of tartar
1 tsp. pure vanilla extract, optional

Hershey’s Milk Chocolate bars, broken into individual pieces, for garnish (optional)
Bite-size graham cracker pieces, for garnish (optional)
Additional graham cracker crumbs, for garnish (optional)

For the cheesecake batter: In a small saucepan, combine the baking chocolate and the heavy cream and heat over low heat, stirring constantly, until the chocolate is melted and smooth; remove from the heat and set aside to cool slightly.
In the mixing bowl of a stand mixer fitted with the paddle attachment, combine and cream cheese, sugar, and cocoa powder and mix on medium-low/medium speed until thoroughly combined and no lumps remain. Scrape the bottom and sides of the bowl, then add the vanilla extract and the chocolate mixture and beat on low/medium-low until well blended and no streaks remain. Finally, add the eggs, one at a time, and beat on low speed until just blended, scraping the sides and bottom of the bowl if needed. Cover the bowl and allow the batter to sit in the refrigerator overnight.
To make the cheesecake: Preheat oven to 350°. In a medium bowl, mix together the graham cracker crumbs and melted butter until thoroughly combined. Lightly press the mixture onto the bottom and partway up the sides of a 9-inch springform pan. Bake for 10 minutes, then allow the crust to cool; Reduce the oven temperature to 325°. 
Pour the cheesecake batter over the crust and place the filled springform pan into a large cake pan or roasting pan, filling the outside pan halfway with water. Place the pan into the preheated oven and bake until the cheesecake is almost set, approximately 1 hour and 30 minutes. Remove the cheesecake from the oven and let it continue to sit in the water bath for about a half hour; remove the springform pan from the water bath and place it in the refrigerator to finish cooling.
For the marshmallow topping: When the cheesecake is completely cooled, place the egg whites, sugar, and cream of tartar in the heatproof bowl of an electric mixer. Set over a saucepan with simmering water and whisk constantly until the sugar is dissolved and the whites are warm to the touch, 3 to 4 minutes. Transfer the bowl to the electric mixer fitted with the whisk attachment, and beat, starting on low speed, gradually increasing to high, until stiff, glossy peaks form, 5 to 7 minutes. Add the vanilla, and mix until combined. Transfer the frosting to a large pastry bag fitted with a large plain round or French tip (I like the Wilton large star tip - #2110). Pipe the frosting in a spiral motion onto the top of the cheesecake, reserving a little extra to pipe around the outside edges and make miniature s’mores, if you’re doing that. Using a kitchen torch, lightly brown the marshmallow topping all around the cheesecake. Pipe some of the remaining topping around the outsides of the cheesecake and sprinkle with extra graham cracker crumbs.
Slice the cheesecake into the desired number of pieces (I think 12 is a nice number) and serve each piece garnished with a piece of Hershey’s candy and bite-size graham cracker pieces. Store any leftover cheesecake, covered well, in the refrigerator.