Cold Cucumber Soup (Oi Naengguk) - Quick Korean Summer Recipe with Dashi

Summer Refreshment in a Bowl: Quick & Easy Cold Cucumber Soup

Cooking time : 10 mins or 70 mins

When the summer heat hits its peak, there’s nothing quite like a bowl of icy, tangy Korean cold cucumber soup (오이냉국, oi naengguk) to cool you down. This dish is a staple in many Korean households during the hot season. It’s refreshing, light, and surprisingly simple to make - especially with a shortcut broth method using dashida.

In this post, I’ll walk you through how I made a super simple yet satisfying version of Cold Cucumber Soup 오이냉국 using a quick dashi broth. It’s a fuss-free recipe that requires no boiling of bones or complex seafood stock. Perfect for beginners or anyone looking to keep the stove time to a minimum during summer!

Why Cold Cucumber Soup?

오이냉국 (oi naengguk) is not just a side dish - it’s a Korean summer ritual. Traditionally served icy cold, this tangy, lightly sweetened broth is poured over crunchy cucumber slices and hydrated seaweed to create a bowl of delicious hydration. It pairs wonderfully with BBQ, rice, or just a simple bowl of noodles.

And unlike hot soups, this one actually makes you feel cooler after eating it. The combination of vinegar, sugar, and chilled temperature is exactly what your body craves when temperatures rise.

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Ingredients for Quick & Easy Cold Cucumber Soup

Here’s what you’ll need for my simplified version of cold cucumber soup:

• 1 liter of water
• 2.5 tablespoons of dashi powder
• 4 tablespoons of sugar
• 4 tablespoons of vinegar (rice vinegar or apple cider vinegar works best)
• 1 cucumber
• A handful of dried seaweed (miyeok)
• Ice cubes (optional, but highly recommended for serving)

This recipe makes about 3 to 4 servings and can easily be doubled for a larger batch.

The Simple Broth Shortcut

Most traditional recipes call for a cooled seafood broth, which often involves boiling anchovies, kelp, and letting it chill for hours. But let’s be real - no one wants to have a boiling pot on the stove for an hour when it’s 90°F (32°C) outside.

So I took the easy route and used dashi powder, a pantry hero in my kitchen. Dashi provides that subtle umami base that makes the broth feel deep and flavorful, without all the effort.

Steps to Make the Broth:

1. In a small pot, combine:
   • 1 liter of water
   • 2.5 tablespoons of dashi powder
   • 4 tablespoons of sugar
   • 4 tablespoons of vinegar

2. Bring it to a light boil and stir until the dashi and sugar are fully dissolved. The broth should taste tangy, slightly sweet, and rich in umami.

3. Let it cool completely, then place it in the refrigerator or freezer for faster chilling.

Tip: If you want your 오이냉국 to be extra icy, place the broth in a stainless steel bowl and pop it in the freezer. Just make sure to take it out before it completely freezes!

Prepping the Vegetables

While the broth is cooling, you can prep the rest of your ingredients.

Cucumber Prep:

• Wash and slice your cucumber into thin, half-moon shapes or julienne it if you prefer a more noodle-like texture.
• Optionally, sprinkle a small pinch of salt and let it sit for 5 minutes, then pat it dry. This helps draw out excess water and keeps the cucumber crunchy.

Rehydrating the Seaweed:

• Place a small handful of dried miyeok (Korean seaweed) in cold water.
• Let it soak for about 10 minutes or until soft and fully rehydrated.
• Drain and cut into bite-size pieces if necessary.

Assembling the Cold Cucumber Soup

Now comes the fun part - putting everything together!

Assembly Steps:

1. In each bowl, add a handful of sliced cucumbers and rehydrated seaweed.
2. Pour in the chilled dashi broth until the ingredients are submerged.
3. Add a few ice cubes for that ultimate summer chill.
4. Optionally, garnish with:
   • Thinly sliced red chili (for a hint of heat)
   • Sesame seeds
   • A drizzle of sesame oil

And there you have it - a gorgeous, refreshing bowl of Cold Cucumber Soup ready to be devoured!

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How to Serve Cold Cucumber Soup

Cold cucumber soup is best served as a side dish or light appetizer. In Korean meals, it’s often enjoyed alongside grilled meat, rice dishes, or even cold noodles like naengmyeon.

You can also enjoy it on its own for a super light lunch. If you’re not very hungry but want something hydrating and nourishing, this is the perfect bowl.

Variations & Tips

Here are a few ideas to customize your Cold Cucumber Soup :

• Add sliced radish for extra crunch and depth.
• Include thin noodles (like somyeon) to turn it into a cold noodle soup.
• Use apple cider vinegar for a bit of fruity sweetness.
• If you like it spicier, add a splash of Korean vinegar-based chili sauce or just a bit of gochugaru (Korean chili flakes).

Storage Tip: The broth can be stored in the fridge for up to 3–4 days. Just add fresh vegetables each time you serve it to keep things crisp and vibrant.

What Makes This Recipe So Great?

• No long simmering required - instant dashi saves time and keeps the kitchen cool.
• Minimal ingredients - most are pantry staples or easy to find.
• Vegan-friendly if you use vegan dashi powder.
• Naturally gluten-free.
• Perfect for meal prep and batch cooking.

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Final Thoughts on Cold Cucumber Soup

As someone who loves Korean food but doesn’t always want to spend hours in a hot kitchen, this quick Cold Cucumber Soup recipe has become one of my go-to summer dishes. It’s not just cooling - it’s flavorful, beautiful, and versatile.

Even if you’re not familiar with Korean cuisine, this recipe is a great place to start. It’s simple, approachable, and doesn’t require specialty cooking skills. Whether you’re serving it alongside a big Korean BBQ feast or eating it solo as a cooling bowl on a hot afternoon, this dish is bound to bring comfort and satisfaction.

If you try this recipe, I’d love to hear what you think - feel free to leave a comment, share your own variations, or tag me on Instagram if you make it!