In a stand mixer, combine milk, water, instant yeast, and granulated sugar. Gradually add flour, melted butter, and salt. Mix well, then knead for 6-8 minutes. Let rise for 15 minutes.

In a saucepan, whisk cocoa powder, heavy cream, chocolate chips, and sugar over low heat until smooth. Stir in crushed graham cracker crumbs and let cool.

Roll the dough into a rectangle, brush with melted butter, spread filling, sprinkle graham crumbs, roll tightly, and slice into pieces.

Preheat oven to 350°F. Arrange rolls in a greased dish and bake for 25-28 minutes until golden brown. Cool for 10 minutes.

Whisk egg whites and sugar over a double boiler until warm. Beat until stiff peaks, gradually adding cream of tartar and vanilla.

Spread meringue over cooled rolls and toast lightly if desired.