In a medium mixing bowl, whisk together the graham cracker crumbs, brown sugar, cinnamon, and salt. Pour in melted butter and toss crumbs until moistened.

Press crumb mixture into the bottom of a 9-inch pie dish. Freeze for 30 minutes while preparing the filling.

In a large bowl combine the chocolate, butter and vanilla. Place a mesh sieve over top and set aside.

To make the filling, in a medium heavy bottomed saucepan set over medium-low heat, add the milk, 1 1/2 cups heavy cream, sugar, and salt. Heat until the sugar has dissolved and the mixture is warm, and gently bubbling.

Meanwhile, in a medium heatproof bowl, whisk together the remaining 1/2 cup of heavy cream, cornstarch and the egg yolks until smooth.

Carefully temper the egg yolks by slowly drizzling the warm mixture into the medium bowl, whisking continuously to prevent the eggs from scrambling. It will take about 5 minutes to incorporate the mixture.

Return the mixture to the stovetop and heat until it reaches 165 degrees on an instant read thermometer and is THICK like pudding. This should take about 5-8 minutes. Pour over the sieve to remove any overcooked pieces of egg that make have formed. Remove the sieve and whisk the milk into the chocolate until melted. As the pudding cools the mixture will thicken.

Pour warm mixture into the chilled crust. Cover with plastic wrap, directly on the pudding. Chill in the refrigerator for 4 hours or overnight until fully set. It should be firm to the touch.

When ready to serve, combine the egg whites, water, corn syrup, granulated sugar, cream of tartar, and salt in the bowl of a stand mixer. Set it over a saucepan with simmering water (medium heat). Whisk constantly until the mixture becomes foamy and reaches 150 degrees. Remove and beat with the whisk attachment on high for 2 minutes, then stop, add the vanilla extract and marshmallows and continue beating for 2 more minutes until the mixture becomes thick and smooth or until stiff peaks form.

Spread over the chilled pie (as much as desired), then toast the top with a kitchen torch and serve immediately.