Some of the best Korean foods are also the oldest. People who love traditional foods that usually have a strong flavor or repulsing appearance are said to have an 아저씨/아재 입맛, or ahjussi taste. Learn about some of these traditional foods below.
곱창 Gopchang or Grilled Small Intestines
Small intestines of a cow or a pig. The word 곱창 by itself usually refers to grilled small intestines, also called 곱창구이. It can also be eaten in a hot pot (곱창전골) or as a sausage (cf. 순대). Prefer 양념곱창 (marinated 곱창) over regular 곱창 if you doubt the quality of the restaurant. 곱창 tastes best with soju.
닭발 Chicken feet
Chicken feet served in a spicy sauce. While their appearance is unattractive at best, chicken feet are really good for the skin as full of collagen. Pair with soju.
말고기 Horse Meat
Very popular in Jeju island, horse meat can be eaten raw (말고기회), grilled (말고기구이), in soup (말고기탕), and in many other ways. Best eaten in Jeju.
번데기 Silkworm Pupae
While the thought of eating silkworm pupae is repulsive, 번데기 is a healthy food, especially rich in calcium. 번데기 can be eaten as a "snack" boiled or steamed, but can also be found in a soup, 번데기탕 as depicted above.
보쌈 and 족발 are respectively boiled pork belly and braised pig's trotters. They are common 안주 dishes (side dishes for alcohol), and best paired with 막걸리.
산낙지 Live Octopus
산낙지 (산낙지탕탕이 as pictured above) is raw octopus killed and cut right before eating; as the nerves are not yet dead the tentacles are still moving. The more the tentacles move, the fresher. See what 산낙지 looks like live on YouTube.
설렁탕 (ox bone soup) and 깍두기 juice
While 설렁탕 by itself does not qualify as ahjussi food per se (cf. picture above), mixing 설렁탕 with the juice of 깍두기 (diced radish kimchi) does qualify as only the experimented ones in 아재입맛 will know this way of eating. 깍두기 has very distinct digestive properties, so make sure not to stay too far from restrooms in the hours following its ingestion.
순대 Sundae or Blood Sausage
A type of blood sausage that has a very distinct pungent smell. 순대 can be eaten by itself but is best enjoyed with 떡볶이 or in soups (순대국/순대국밥 for example).
육회 (肉膾) Yukhoe or Shredded Raw Meat
Shredded meat (typically beef) served raw. The typical 육회 is served with an egg yolk and Korean pear. Best paired with 막걸리. To qualify as a real 아저씨, eat 육회 at one of the restaurants inside 광장시장 in Seoul.
장어 (長魚) Eel
장어 (eel) is a very delicate fish in Korea, said to be good for men... Eel in Korea is mostly eaten grilled (장어구이), but can also be cooked in soups and, contrary to popular belief and misinformation from Wikipedia, can be also eaten raw in the case of freshwater eel (민물 장어회) prepared in specialty restaurants (although rare in Seoul). Note that 꼼장어 (hagfish) is totally different from 장어 although they share two characters. Learn more about 장어 (eel).
회 (膾) Hoe or Raw Meat/Fish
Raw fish or meat, similar to Japanese sashimi except that the fish is supposed to be killed right before eating, and is served with many side dishes. Best paired with 소주 or 청하 (Korean sake). 노량진수산시장 (Noryangjin Wholesale Market) is a good place to indulge in 회 in Seoul.
This list could not be complete without mentioning other typical 아재입맛 dishes: 홍어회 (skate hoe with a very pungent smell), 청국장 (fermented soybean soup, also with a pungent smell), 생간 (生肝; raw liver), and 돼지 껍데기 (pork rinds), among many other dishes. The dishes I have included in this post were all tried and photographed by myself; I will update this post as my 아재입맛 develops further.
If you want to order these delicious foods while in South Korea, make sure you know the appropriate vocabulary for food survival.
This list was inspired by a test that you can take here: https://post.naver.com/viewer/postView.nhn?volumeNo=16163074&memberNo=23332686, and from this page https://1boon.kakao.com/linkagelab/uncle_taste.