Crust: Preheat oven to 350 degrees. In a food processor, pulse graham crackers until finely ground. Add flour, salt, butter, and sugar; pulse to combine. Transfer mixture to another rimmed baking sheet and bake 10 minutes. Coarsely chop until no large clumps remain. Bake 10 minutes more. Remove and chop again; set aside to cool.
Mousse Filling: Add egg yolks to a stand mixer with the whisk attachment. On the highest speed whisk yolks 3-4 minutes until they thicken.
Meanwhile, warm half of the heavy cream in a medium saucepan. Do not boil. Once warm, add a small bit of the cream to the egg mixture while stirring to temper the eggs. Once incorporated add the egg mixture to the saucepan with the rest of the warm cream, stirring to incorporate. Cook the mixture over medium-low heat until thickened, roughly a minute or two. Take off the heat and add the chocolate stirring until melted and incorporated into the custard then mix in the chocolate balsamic. Let cool completely
Add the remaining heavy cream to the stand mixer with the whisk attachment. Whisk until cream forms soft peaks. Very carefully fold the whipped heavy cream into the cooled chocolate custard mixture. Refrigerate until ready to assemble dessert.
Marshmallow Cream Topping: Add egg whites, granulated sugar and cream of tartar to a heat proof bowl of an electric mixer. Set bowl over a saucepan filled with a few inches of simmering water. Heat mixture, whisking constantly until egg whites are very warm to the touch, about 4 minutes (mixture so register 160 degrees on a candy thermometer).
Remove from heat and transfer bowl to electric stand mixer fit with a whisk attachment. Beat mixture beginning on low speed and gradually increasing to high speed, until stiff glossy peaks form, about 6 - 8 minutes. Add vanilla vinegar during the last 10 seconds of mixing.
To assemble the dessert, place a bit of the graham cracker crust in the bottom of each individual serving dish. Pipe equal amounts of the chocolate mousse over the crust. Then pipe with the marshmallow cream topping to fill the serving cup. Using a kitchen torch, brown the top of the marshmallow cream topping just before serving. Top with a sprinkle of the crust mixture or, some Ritual chocolate shavings, and some of the chocolate chip stuffed marshmallows chopped into small pieces for garnish.