Bibim Guksu (Spicy Korean Cold Noodles)

Why noodles turn gummy, and how to stop it: Dried wheat noodles shed starch as they boil, and that starch turns sticky as the noodles cool. Four habits keep them silky. Use plenty of water (at least 2 quarts / 2 liters for 7 oz / 200 g of noodles) and stir for the first 30 seconds so the strands do not stick together. Cook them only until just tender, because very thin noodles go from perfect to soft in under a minute, so taste early. Rinse thoroughly under cold running water, rubbing the noodles gently between your hands until the water runs clear; skipping this is a common reason home versions taste gluey. And drain them well, since water left on the noodles dilutes the sauce and leaves the dish pale and bland.

Toss at the last minute: The noodles keep absorbing the sauce, so toss them only when you are ready to eat. If you need to wait more than 10 minutes, leave the rinsed noodles plain in the colander and keep the sauce in its bowl. If the noodles have clumped by then, dunk them in cold water for a few seconds, loosen them with your fingers, drain them again and toss them with 1 tsp of sesame oil before adding the sauce. Do not leave cooked noodles out for more than 2 hours (1 hour above 90 F / 32 C); cover and refrigerate them if you need to wait longer.

Fixing the sauce: Taste the sauce before it meets the noodles, since it is easier to fix in the bowl. If it tastes too sharp, stir in 1 tsp of sugar or syrup. If it is too sweet, add 1 tsp of vinegar. If it tastes flat, add a splash of soy sauce rather than plain salt. If it is too hot, add 1 tsp each of sugar and sesame oil and pile on extra cucumber; the egg yolk helps too. Gochujang is already salty and brands vary a lot, so add soy sauce a little at a time.

Spice level: As written, the sauce is medium: warm and noticeable, but not painful. Gochujang brands range from mild to quite hot, so taste a small dab first. For a milder bowl, leave out the gochugaru, use 1 1/2 tbsp of gochujang and add 1 extra tsp of syrup. If you are feeding someone who is wary of chili, serve the sauce in a small bowl on the side. For a hotter bowl, add up to 1 more tbsp of gochugaru or a thinly sliced fresh green chili. Do not swap in regular crushed red pepper flakes for gochugaru, since they are much hotter; if you have no gochugaru, leave it out and use 2 1/2 tbsp of gochujang. Gochujang is sold in tubs in the Asian aisle of many large supermarkets and online, and it has no true substitute here.

Choosing noodles: Look for somyeon at Korean and other Asian grocery stores. Japanese somen is a very similar noodle, is sold in many supermarkets and works well, but check the package time because brands differ. In a pinch, use thin spaghetti, angel hair or capellini: cook it until just tender and rinse it well. The texture will be firmer and less delicate. For a chewier bowl, try jjolmyeon (thick, chewy wheat noodles sold at Korean markets) or udon, and follow their package times. Naengmyeon noodles are a different kind of noodle (chewier, made from buckwheat or starch) and cook differently, so use their own package directions if you try them. The same thin wheat noodles are used for janchi guksu, often translated as banquet noodles, which is served in a warm anchovy broth.

About the kimchi: Well-fermented, sour kimchi suits this sauce best, because its tang matches the vinegar. Fresh kimchi works too, but it tastes milder and crunchier. If you have made our Easy Kimchi, use a batch that has turned clearly sour, and save any extra for Kimchi Fried Rice. The kimchi is optional; the noodles are good with just cucumber and egg.

Dietary notes: As written, this recipe contains wheat (the noodles, the soy sauce and, in many brands, the gochujang), egg, soy and sesame. It is vegetarian only if the labels on your kimchi and gochujang list no fish, shellfish or meat, because many kimchi brands contain fish sauce or salted shrimp. For a vegan bowl, also skip the eggs, use maple syrup or agave instead of honey, and check the kimchi label for fish, shellfish and meat. Somyeon, somen, udon and spaghetti are all made with wheat, so this is not a gluten-free dish as written. If you avoid gluten, look for noodles labeled gluten-free (some rice noodles qualify, but many soba and other buckwheat noodles contain wheat flour), use tamari or a soy sauce labeled gluten-free, and read the gochujang and kimchi labels for wheat and barley.

Make ahead and storage: The sauce keeps in a covered jar in the fridge for up to 1 week; stir it before using. Eggs can be boiled up to 2 days ahead and kept unpeeled in the fridge. For 4 servings, double everything and cook the noodles in 4 quarts (4 liters) of water in a pot of at least 6 quarts (6 liters), or in two batches. The finished noodles are best eaten right away. If you have leftovers, refrigerate them within 2 hours (1 hour above 90 F / 32 C) and eat them the next day; the noodles will be firmer and the cucumber watery, so loosen them with a splash of cold water and add fresh cucumber. Freezing is not recommended. For a packed lunch, carry the plain rinsed noodles and the sauce in separate containers, keep them cold with an ice pack, and toss just before eating; if they cannot be kept cold, eat them within 2 hours (1 hour above 90 F / 32 C).

Variations: For a kimchi-forward bowl, double the kimchi to 1 cup (about 150 g) and stir 1 tbsp of its juice into the sauce. For a version with no chili, skip the gochujang and gochugaru and toss the noodles with 3 tbsp soy sauce, 1 tbsp sugar, 1 tbsp sesame oil, 1 tsp vinegar and the garlic; taste, and add 1 tbsp cold water if it is too salty. For a heartier meal, add shredded poached chicken or thin slices of boiled pork. Lettuce, perilla (kkaennip) leaves and carrot matchsticks are easy extra vegetables, and a spoonful of Kongnamul Muchim or Korean Spinach Side Dish on top adds a seasoned vegetable without extra work. A halved egg from our Mayak Eggs recipe can replace the plain boiled egg. Grating 2 tbsp of apple or Asian pear into the sauce adds a fresh sweetness. The photo on this page shows a bowl topped with cucumber, chopped dark greens and sesame seeds, without the boiled egg that the recipe above uses.

What to serve with it: Bibim guksu is a light meal by itself, but something mild and savory balances the heat. Gyeran Mari (rolled omelette) and Pajeon (scallion pancake) are easy choices, and Kimbap makes it a fuller lunch. If you like the sweet-spicy gochujang flavor here, try Tteokbokki or Jeyuk Bokkeum next, and for a noodle dish with no chili at all, try Japchae.