In a stand mixer, combine lukewarm milk, lukewarm water, instant yeast, granulated sugar, and all-purpose flour. Add melted unsalted butter and salt. Mix until well combined.

Switch to the hook attachment and knead for 6-8 minutes until the dough is smooth and elastic. Cover and let it rest for 15 minutes to rise slightly.

In a saucepan over low-medium heat, whisk together cocoa powder, heavy whipping cream, semi-sweet chocolate chips, and granulated sugar. Add melted unsalted butter, vanilla extract, and a pinch of salt. Stir until smooth and well combined, then remove from heat. Cool and mix in graham cracker crumbs.

On a lightly floured surface, roll the dough into a 10” x 16” rectangle. Brush with melted butter, then spread the cooled filling evenly over the dough, leaving edges clear. Sprinkle graham cracker crumbs, roll tightly, slice into 8-10 pieces, and arrange in a greased baking pan.

Preheat your oven to 350°F (175°C). Bake the rolls for 25-28 minutes until golden brown. Cool in the pan for 10 minutes before adding meringue.

In a double boiler, combine egg whites and granulated sugar. Whisk continuously until the mixture is warm and sugar dissolves. Transfer to a stand mixer and beat until stiff peaks form, adding cream of tartar, salt, and vanilla extract.

Spread the meringue on top of the baked rolls and use a kitchen torch or broiler to toast until golden brown.