In a stand mixer, combine lukewarm milk, water, yeast, sugar, flour, melted butter, and salt. Mix on low until combined, then knead on medium speed for 6-8 minutes until smooth and elastic. Let the dough rest in a warm place for 15 minutes.

In a saucepan over low heat, combine cocoa powder, heavy whipping cream, chocolate chips, melted butter, vanilla extract, and salt. Stir until smooth, then mix in graham cracker crumbs. Allow it to cool slightly.

Roll the rested dough into a 10” x 16” rectangle. Brush with melted butter, spread filling evenly, sprinkle with extra graham cracker crumbs, roll tightly, and cut into 8-10 pieces. Place in a greased baking dish.

Preheat oven to 350°F (175°C). Bake rolls for 25-28 minutes until golden brown and puffed. Cool for 10 minutes.

Whisk egg whites and sugar in a heatproof bowl over a double boiler until warmed. Beat until stiff peaks form, adding cream of tartar and vanilla extract.

Spread meringue over rolls, then lightly toast using a kitchen torch or broiler until golden brown. Allow to set for a minute before serving.