The black-noodle lunch Koreans order on moving day, and where it began

The buzzer sounds at the new apartment before the boxes are open, and a man in a helmet hands over a stack of steel tins still warm from the scooter. Inside are four bowls capped in cling film, a black slick of sauce over noodles, a small dish of yellow pickle and raw onion beside each. This is what a Korean move looks like at noon — not a restaurant meal, but jajangmyeon (짜장면) delivered to a floor that has no furniture on it yet.

The restaurant tourists walk past

Every Korean neighbourhood has a junggukjip (중국집), a Korean-Chinese restaurant, usually behind a red sign and a laminated menu you could read in the dark because it never changes. Visitors tend to pass it on the way to the barbecue place or the bibimbap counter, because it does not look like the Korea in the brochure. Locals treat it as infrastructure. You order from it on moving day, after exams, on the fourteenth of April — Black Day (블랙데이), when people without a partner eat black noodles together and call it a joke that everyone still shows up for.

The room is rarely built for lingering. Formica tables, a television bracketed high in one corner, a water dispenser you serve yourself, and a stack of steel delivery boxes — cheolgabang (철가방) — by the door, waiting for the next run. A plain bowl of jajangmyeon runs about 7,000 won; jjamppong (짬뽕), its spicy seafood cousin, is usually 9,000 to 10,000. The prices are printed small because they are the least interesting thing in the room.

Reading the black-noodle menu

Jajangmyeon is wheat noodles under a sauce built from chunjang (춘장), a fermented black-soybean paste darkened with caramel, fried down with diced pork, onion and a little potato until it turns glossy. The standard bowl arrives already mixed. Ask for ganjjajang (간짜장) and the sauce comes stir-fried to order in a separate dish, drier and sharper, for you to fold in yourself. Samseon jajang (삼선짜장) swaps in squid and shrimp; jaengban jajang (쟁반짜장) is stir-fried on a wide platter for the table to share.

The other half of the menu is jjamppong, a red broth loud with chilli oil, mussels, squid and cabbage over the same noodles. Choosing between the two is a small national pastime — someone at the table always wants both, which is why any junggukjip will quietly split a portion of each into two bowls if you ask. There is also a milder white version, baek-jjamppong (백짬뽕), for anyone who finds the red one merciless.

짜장면이냐 짬뽕이냐, 그 사소한 고민이야말로 한국 사람이 중국집 앞에서 늘 하는 일이다.

Tangsuyu, and the argument that comes with it

No table of two orders noodles alone. The third dish is almost always tangsuyu (탕수육), pork battered and fried twice, served with a translucent sweet-and-sour sauce full of carrot, cucumber and wood-ear mushroom. A small platter is around 18,000 to 20,000 won, enough for two to share. It arrives with the sauce on the side, and that is where the argument starts.

Koreans divide, only half-jokingly, into two camps. Bueomeok (부먹) pour the sauce over the whole plate so the batter goes soft and drinks it in. Jjigmeok (찍먹) keep the pork crisp and dip each piece as they eat. People hold the preference the way they hold a football team. The safe move, if you are hosting, is to leave the sauce on the side and let everyone commit their own crime.

Where the black sauce comes from

The dish is Korean, but its address is Incheon (인천). When the port opened in 1883, labourers and merchants from Shandong settled the hill above the harbour, and the food they cooked for dock workers — cheap noodles under fried bean paste — slowly became something neither wholly Chinese nor Korean. The restaurant usually credited as its birthplace, Gonghwachun (공화춘), still stands in Incheon's Chinatown; the building now holds the Jajangmyeon Museum (짜장면박물관), where a recreated kitchen and old delivery boxes trace how a Shandong sauce became the sound of a Korean moving day.

You reach the quarter from Incheon Station (인천역) on the dark-blue Line 1; exit 1 faces the painted paifang gate across the road. The hill behind it is a twenty-minute climb of red staircases, mural walls and shops selling gonggal-ppang (공갈빵), a hollow sugar bread the size of a fist. The museum charges 1,000 won. Most restaurants up the slope will seat you for the same 8,000-won bowl you would get anywhere, with the harbour added to it.

Ordering one for yourself

If you want the everyday version rather than the tourist hill, walk into any junggukjip near where you are staying between noon and two. Point at jajangmyeon or jjamppong on the wall, hold up fingers for how many, and a bowl lands in front of you within ten minutes. The danmuji (단무지), the sliced raw onion and the ramekin of chunjang to dip it in are free and endlessly refilled, and so is the water. Nobody tips.

Two things trip up visitors. The first is expecting the Chinese restaurant of back home — this is its own cuisine, and asking for anything authentically Sichuan will only puzzle a kind cook. The second is delivery: most shops set a minimum of two dishes or around 15,000 won, and will not hunt for a guesthouse stairwell they cannot place, so eating in is simpler. Order the noodles you can finish, split a tangsuyu if there are two of you, and leave the sauce on the side. The rest is only choosing your camp.