Preheat the Oven: Preheat your oven to 375°F (190°C).
Prepare the Pan: Pour the melted butter into the bottom of a 9x13-inch baking dish and spread it evenly.
Prepare the Cinnamon Rolls: Open the can of Pillsbury Hot Cocoa Grand Cinnamon Rolls. Set the icing aside for later. Cut each cinnamon roll into quarters and arrange the pieces evenly over the melted butter in the pan.
Make the Cocoa Custard: In a medium mixing bowl, whisk together the eggs, heavy whipping cream, granulated sugar, cocoa powder, and vanilla extract until smooth.
Assemble the Bake: Pour the custard mixture evenly over the cinnamon roll pieces, ensuring they are well-soaked. Sprinkle the chocolate chips on top.
Bake: Bake uncovered for 25 minutes. Then, remove the foil and bake for an additional 15 minutes, or until the top is golden brown and the custard is fully set.
Cool and Drizzle Frosting: Let the bake cool for 10 minutes. Drizzle the reserved frosting evenly over the top.
Top with Marshmallow Fluff and Torch: Spread a generous layer of marshmallow fluff over the frosting. Use a kitchen torch to lightly toast the marshmallow fluff until golden brown and slightly charred in spots. If you don’t have a torch, place the dish under the broiler for 1–2 minutes, keeping a close eye to avoid burning.
Serve: Dust the toasted marshmallow fluff with cocoa powder for a final chocolatey touch. Slice and serve warm!