Cháshāo Bāo (Open) (叉烧包开口) is the open-topped barbecue pork bun: char siu served in a split steamed bun rather than fully enclosed, so the meat sits exposed at the top instead of sealed inside. The angle is presentation and ratio. By splitting the bun and laying or spilling the filling at the crown, this form puts the char siu in plain view and shifts the eating experience toward something closer to a soft bun cradling meat than a sealed package. It rewards a filling that looks and tastes good on its own, because there is no dough lid hiding it, and a steamed bun soft enough to act as a tender base.
The build keeps the steamed-bun foundation but changes the closure. The dough is the same enriched, lightly sweetened wheat dough used for the enclosed version, proofed and steamed to a soft, pale crumb. Rather than being pleated fully shut, the bun is either left open at the top with the filling visible at the crown, or steamed plain and split to receive the char siu after cooking. The char siu is roast pork, sliced or diced, glossy with its sweet-savory lacquer, sometimes loosened with a little reduced sauce so it holds together without running. Good execution shows in the contrast being legible: a bun that is soft and springy without being wet, meat that is moist and clearly the focus since it is on display, and just enough sauce to bind without flooding the open crumb. Sloppy versions are obvious because nothing is hidden. Dry or scarce char siu looks and eats poorly when it is right there at the top. Too much loose sauce runs down the sides and turns the bun soggy. A dense, underproofed bun reads heavy under the exposed meat, and an overfilled crown topples and falls apart in the hand.
It shifts mostly by how the meat is cut and how generously it sits at the top. A neatly arranged few slices reads tidy and restrained; a heaped, slightly spilling crown reads abundant and street-style. The fully enclosed steamed bun and the baked, glazed version are distinct preparations built on the same filling but different closures and crusts, and each deserves its own article rather than being folded in here. The open form sits conceptually near the gua bao idea of a soft bun holding visible meat, though it is its own thing. Like its enclosed sibling it is meant to be eaten hot, the warm soft dough against the sweet pork, often as part of a larger dim sum or bun spread rather than alone.