In a medium saucepan over medium heat, bring the cream, milk, sugar and salt to a simmer. In a medium mixing bowl, whisk the egg yolks.
Temper the egg yolks by slowly whisking in half of the cream mixture into the egg yolks in a thin, steady stream. Whisk the tempered mixture back into the remaining cream mixture.
Return the pot to the heat and continue to cook, stirring constantly, until the mixture is thick enough to coat the back of a spoon.
Remove the pot from heat and whisk in the chocolate until it is entirely combined, about 5 minutes.
Pour about 3 tablespoons of the graham cracker crumbs into each of the cups or ramekins. Divide the custard among the cups then cover and refrigerate until the custard has set, about 2 hours.
For serving:
Use a kitchen torch to quickly torch the top of the meringue cookies to add a smokey s'mores flavor (optional).
Top with the remaining graham cracker crumbs, and meringues. Serve chilled.