Take a melon pan, split it across the middle while it is still slightly warm, and wedge a scoop of ice cream into the gap, and the bakery roll becomes a street snack. This is the handheld form of the cookie-crust bun: the same scored shell that cracks into a netted, melon-rind pattern, the same soft enriched body underneath, but now built around a cold core that starts melting the moment it meets the warm crumb. It is eaten walking, from a paper sleeve, and the whole appeal is the temperature clash. The roll signs the name with its crackled top; the ice cream is what the line is for.
The craft is a race against melt, and it depends on getting the bun right first. The base follows the standard form: a thin sweet cookie sheet draped over a tender enriched bread ball, scored and baked so the top fractures into sandy shards while the body stays light and airy. For this version the roll is often warmed or griddled so the shell crisps again, then sliced part way through so it opens like a clam and holds the scoop without spilling. The ice cream is usually a firm vanilla or matcha, dense enough to keep its shape against the heat for the minute it takes to eat. The skill is in the gap between hot and cold being narrow and deliberate: a shell crisp enough to crackle, a crumb warm enough to contrast the scoop, and a scoop firm enough that the first bites are clean before the melt arrives and the last bites turn happily messy. Done well it is a controlled collapse, crisp top, warm soft body, cold sweet center, the textures peeling apart in sequence. Done poorly the bun is cold and claggy, the ice cream is icy or already soup, and the thing slides out the back onto the pavement.
Because the melt clock is short, this is firmly a buy-and-eat-now item rather than anything that survives a bag or a chiller. It eats richer and colder than a plain melon pan, sweeter too, and reads as a dessert on the move rather than a snack roll.
The variations are mostly a question of what goes in the gap. Vanilla and matcha are the common pair; shops also run chocolate, hojicha, fruit, or soft-serve piped tall through the split so it spirals above the crust. Some toast the shell darker for extra crackle against the cold; some swap the body for a chocolate-tinted melon pan to match the scoop. The plain unfilled roll, where the whole point is the bare crack of the shell with nothing inside it, deserves its own article rather than being crowded in here.