Dough 

1. In a mixing bowl, combine the warm milk, a pinch of sugar, and the active dry yeast. Stir until dissolved and let it sit for 8–10 minutes, or until it becomes foamy.
2. To the yeast mixture, add the egg, all-purpose flour, granulated sugar, salt, and softened butter. Knead for about 15-20 minutes until the dough is soft, smooth, and elastic.
3. Let the dough proof for 1 hour and 30 minutes in a warm spot at around 27°C (80–85°F), or until doubled in size.

Assemble

1. Prepare a mixture of cocoa powder and granulated sugar, and sift the cocoa powder to avoid big lumps. 
2. Roll out the dough into a rectangle. Spread the softened butter evenly over the surface. Sprinkle the cocoa-sugar mixture, add crushed graham crackers, and chocolate chips on top. Cut the dough into strips with a knife, then roll each strip individually.
3. Place the shaped rolls in a baking pan. Cover and let them proof again for 30 minutes at around 27°C (80–85°F), until puffy.
4. Preheat the oven to 180°C (350°F). Pour the heavy whipping cream over the rolls. Bake for 20–25 minutes, checking at the 20-minute mark, until golden brown.
5. Immediately top the warm rolls with marshmallows and toast them lightly. Let the rolls cool slightly before serving