Cold Soy Milk Noodles: Rich Kongguksu Recipe

Seoul in July is humid enough to make your shirt stick to your back the second you step outdoors. When the heat hits that oppressive summer peak, my grandmother used to pull out a giant stainless steel bowl filled with yellow soybeans soaking in cool water. She knew that nothing cools down an overheated body quite like a bowl of kongguksu (cold soy milk noodles).

Prep: 20 min  ·  Cook: 10 min  ·  Total: 30 min  ·  Serves 4

Kongguksu is a classic Korean summer dish featuring thin wheat noodles served in a freshly blended, velvety broth made from whole soybeans, nuts, and seeds. In Korea, we view this not just as a light lunch, but as a form of boyangsik (restorative summer food) that replenishes lost energy without burdening the stomach. The broth is rich, nutty, and naturally creamy without containing a single drop of dairy. Paired with a side of sharp, cold baechu kimchi (napa cabbage kimchi), it is one of the most satisfying noodle dishes you can make at home.

Making this dish from scratch outside Korea might sound intimidating, but it requires only a few basic pantry staples. The secret lies entirely in how you handle the soybeans—cook them too little and they taste grassy; cook them too long and they taste like bean soup. Here is how to master the technique in your own kitchen.

Why This Works

• Strict boiling window: Cooking the soaked soybeans for precisely 5 to 7 minutes removes the raw, grassy enzyme odor while preserving the fresh, naturally sweet flavor of the bean.
• Nut and seed emulsion: Blending toasted white sesame seeds alongside pine nuts or peanuts introduces healthy oils that blend with the soy protein, yielding an ultra-creamy, milk-like body.
• Ice-shocked noodle rinse: Vigorously washing cooked wheat noodles in cold water strips away surface starch, preventing the noodles from absorbing broth prematurely and giving them a springy texture.

Ingredients

• 200 g (about 1 cup) dried yellow soybeans
• 30 g (about 1/4 cup) pine nuts or unsalted roasted peanuts
• 30 g (about 3 tbsp) white sesame seeds, toasted
• 1000 ml (about 4 cups) cold filtered water, plus extra for blending
• 350 g (about 12 oz) dry somyeon (thin wheat noodles)
• 1/2 English cucumber, thinly sliced into matchsticks
• 1 medium ripe tomato, sliced into wedges
• 1 tsp fine sea salt (plus extra for individual serving)
• Ice cubes for serving

Substitutions

If you cannot find traditional Korean somyeon (thin wheat flour noodles), Japanese somen is identical and readily available in most Western supermarkets. In a pinch, thin angel hair pasta works well—just add a quarter-teaspoon of baking soda to the boiling water to give the pasta a springier, Asian-noodle texture.

For the nut blend, pine nuts offer a subtle, luxurious sweetness. However, unsalted roasted peanuts, raw cashews, or blanched almonds work wonderfully as realistic Western swaps. If you have a nut allergy, double the toasted white sesame seeds instead.

How to Make It

1. Soak the soybeans (8 to 12 hours): Rinse 200 g (about 1 cup) of dried yellow soybeans thoroughly under cold running water. Place them in a large bowl, cover with at least 3 inches of cold water, and let them rehydrate overnight at room temperature. Why: Fully rehydrating the beans ensures they cook evenly to the core, preventing a grainy texture when blended later.
2. Boil the beans briefly (5 to 7 minutes): Drain the soaked beans and transfer them to a medium pot. Cover with clean water (about 2 inches above the beans) and bring to a rolling boil over high heat. Once boiling, skim off any white foam and cook for exactly 5 to 7 minutes. Why: Under-boiled beans taste unpleasantly grassy and raw (a smell known as beorin mat in Korea), while over-boiled beans taste like soybean paste soup. You want them tender yet firm, like cooked green peas.
3. Drain and rinse thoroughly: Drain the beans immediately in a colander and rinse under cold running water to stop the cooking process. As you rinse, gently rub the beans between your hands. Why: Rubbing loosened clear skins away allows you to float and wash them off. Removing excess skins produces a dramatically smoother soy milk broth.
4. Blend until completely smooth: Transfer the rinsed beans to a high-speed blender. Add 30 g pine nuts, 30 g toasted sesame seeds, 1 tsp sea salt, and 1000 ml cold filtered water. Blend on high speed for 2 to 3 full minutes until completely liquid and velvety. Why: High-speed blending emulsifies the natural fats in the nuts and seeds with the soybean protein, creating a thick, rich broth without needing dairy or cream.
5. Chill the soybean broth: Pour the blended soy broth into an airtight glass container and chill in the refrigerator for at least 2 to 3 hours until icy cold. Why: Kongguksu broth loses its refreshing contrast if served warm or room temperature; chilling allows the nutty flavors to settle and harmonize.
6. Boil and wash the noodles: Bring a large pot of water to a boil. Add 350 g of somyeon noodles and cook according to package instructions (usually 2 to 3 minutes). When the pot foams up, pour in a splash of cold water to bring the foam down. Drain noodles into a colander and immediately rub them briskly under cold running ice water. Why: Friction under cold water washes away excess surface starches that make noodles gummy, yielding a springy texture (teng-teng) that stays firm in cold soup.
7. Assemble and serve: Divide the chilled, drained noodles into deep serving bowls. Pour the chilled soybean broth over the noodles until submerged. Top with cucumber matchsticks, tomato wedges, and a few ice cubes. Serve immediately with extra salt on the side. Why: Salting at the table allows each person to adjust to their taste without causing the broth to break or separate beforehand.

Tips from a Korean Kitchen

In my family, we never salt the entire pitcher of soy milk in advance. Salt draws out moisture and can break down the smooth emulsification of freshly blended bean milk, causing it to separate into watery layers in the fridge. Always keep the batch unsalted, pouring individual bowls and letting diners stir in fine sea salt right before taking their first bite.

Pay close attention to sensory cues while boiling the soybeans. As the pot reaches a boil, step close and smell the steam. In the first 2 minutes, it will smell distinctly like raw green beans. By minute 5, that raw aroma turns into a pleasant, sweet, nutty fragrance similar to steamed edamame. That transition is your sign to pull the pot off the stove.

Finally, pair this dish with crisp side dishes. Because kongguksu is delicate and creamy, serving it alongside tangy kkakdugi (cubed radish kimchi) or fresh geotjeori (unfermented summer kimchi) creates a delightful contrast in texture and acidity.

Storage

Store the pureed soy broth in a clean glass jar or sealed container in the refrigerator for up to 3 days. Do not freeze the broth, as freezing breaks the oil-water emulsion and renders the milk grainy upon thawing. Always cook noodles fresh on the day of serving; leftover cooked somyeon becomes soggy quickly when stored in liquid.

FAQ

Can I make kongguksu using store-bought soy milk or tofu?

Yes, you can make a quick version! Blend 1 block of drained silken or firm tofu with 2 cups of unsweetened plain soy milk, 2 tablespoons of peanut butter or toasted sesame seeds, and a pinch of salt until smooth. While this shortcut lacks the deep complexity of whole boiled soybeans, it makes a rich and satisfying cold noodle meal in under 10 minutes.

Why is my homemade soybean broth grainy?

A grainy texture usually stems from two factors: an underpowered blender or leaving too many bean skins on before blending. To fix this, either blend for a longer duration (3 full minutes on high speed) or pass your blended soy milk through a fine-mesh sieve or cheesecloth before chilling.

Do Koreans eat kongguksu with salt or sugar?

This is a famous culinary debate in South Korea! In Seoul and Northern regions, kongguksu is almost exclusively seasoned with fine sea salt to highlight its savory, nutty flavor. However, in Jeolla Province and Southern regions, it is common to add a spoonful of white sugar for a sweet, dessert-like noodle soup. Try a pinch of both in small bites to see which style you prefer!

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• Bibim Guksu Recipe: Spicy Cold Noodles for Sizzling Summer Days (비빔국수)
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