In a stand mixer, combine milk, water, instant yeast, and granulated sugar. Gradually mix in all-purpose flour, then add melted unsalted butter and salt. Knead for 6-8 minutes. Let rise for 15 minutes.

In a saucepan over low-medium heat, whisk together cocoa powder, whipping cream, chocolate chips, and sugar until smooth. Remove from heat and mix in melted butter and graham cracker crumbs. Let cool.

Roll out the dough into a rectangle. Brush with melted butter.

Spread the filling evenly over the dough, then roll tightly and cut into 8-10 pieces. Place in a greased baking pan.

Preheat oven to 350°F. Bake for 25-28 minutes until golden brown. Let cool slightly.

In a double boiler, combine egg whites and sugar, whisk until warm and sugar dissolves. Beat until stiff peaks form. Add cream of tartar and vanilla extract.

Spread meringue over rolls and toast lightly with a kitchen torch or broiler until golden.