In a large mixing bowl, combine 1 cup of lukewarm milk and 1/4 cup of lukewarm water, then sprinkle in 2 1/4 teaspoons of instant yeast and 1/4 cup of granulated sugar. Stir to dissolve, then gradually add in 3 3/4 cups of all-purpose flour, 4 tablespoons of melted unsalted butter, and 1 teaspoon of salt. Knead the dough on a floured surface for about 6–8 minutes until it’s smooth and elastic. Cover and let it rise for 15 minutes.

For the filling, take a medium saucepan and heat 1/8 cup of unsweetened cocoa powder, 1/8 cup of heavy whipping cream, and 1/3 cup of semi-sweet chocolate chips over low heat. Stir continuously until the mixture is smooth and creamy, ensuring the chocolate fully melts. Once combined, remove the pan from heat and let it cool slightly before folding in 1/4 cup of graham cracker crumbs to add texture.

Once the dough has risen, roll it out into a large rectangle on a floured surface, aiming for about 1/4 inch thickness. Brush the dough generously with the remaining melted butter, then evenly spread the chocolate filling over the surface, followed by an additional sprinkle of graham cracker crumbs. Carefully roll the dough tightly from one end to the other, and slice the log into even pieces using a sharp knife.

Preheat your oven to 350°F (175°C). Arrange the sliced rolls in a greased baking dish, leaving some space between them for expansion. Bake in the preheated oven for 25–28 minutes, or until the rolls are golden brown on top and the dough has fully cooked. Once done, remove them from the oven and let the rolls cool for around 10 minutes before adding the meringue.

While the rolls are cooling, prepare the meringue by placing 2 large egg whites in a heatproof bowl set over a pot of simmering water (double boiler). Add 1/8 teaspoon of cream of tartar and whisk gently until the egg whites are warm and the sugar dissolves completely. Remove from heat and beat with a mixer until stiff peaks form, then gently mix in 1/2 teaspoon of vanilla extract.

Finally, spread the meringue generously over the warm gooey s'mores rolls, ensuring even coverage. Use a kitchen torch to lightly toast the meringue until it turns golden brown, taking care to move the flame continuously to avoid burning. Serve the rolls warm and enjoy the delightful contrast of textures and flavors!