Oi‑naengguk (오이냉국) is a simple, refreshing Korean summer soup made with chilled cucumber slices in a lightly tangy, savory‑sweet broth. It’s traditionally served as a small side dish that helps cut through heat and humidity, offering a clean, cooling contrast to richer foods. In our restaurant, we often brought it out as a little bonus on hot days—a small gesture that guests appreciated and that echoed the easy generosity of Korean home cooking. Whether enjoyed with rice, alongside barbecue, or on its own, oi‑naengguk captures the straightforward, cooling comfort of a Korean summer.

  
Ingredients
1 medium Cucumber (about 1 1/2 cups - 7 ounces)
3 cloves garlic
1 medium green onion
1 green chili pepper
1 red hot chili pepper
6 ice cubes

Broth:
1 1/2 tablespoon vinegar
1 teaspoon salt
1 teaspoon fish sauce
1 teaspoon sugar
1 1/2 cup cold water

Directions:

Preparation:
Wash cucumber in cold water.
Slice the cucumber in half crosswise, then thin slice (about 1/8" thick) each half lengthwise.
Cut slices lengthwise into "noodles" about 1/8" thick. (Julienne)
Place cucumber strips into a medium mixing bowl.

Mince, fine chop, or thin slice the garlic cloves and add to the bowl.
Cut the green chile pepper into thin slivers and add to the bowl.
Cut the green onion into roughly 1/4 inch segments and add to the bowl.
Gently toss the contents of the bowl until well mixed.

Mix Broth
In a separate bowl, mix all broth ingredients until sugar and salt are dissolved.

Final:
Separate the cucumber mix into two equal portions and place into serving bowls.
Fine chop the red chili pepper.
Pour one half of the broth over each serving.
Sprinkle red pepper into each bowl, add ice cubes, and serve.

Variation:
Mix the broth before prepping the vegetables. Pour broth into an ice tray and freeze.
Add one additional cucumber, then slice both in half lengthwise. Remove the pulpy seed area and reserve it, then julienne as above.
Prep vegetables as above and divide into serving bowls.
Place the frozen broth cubes into a strong blender, add one or two tablespoons water, and blend into slush.
Mix the cucumber pulp into the slush.
Spoon the slush equally into the serving bowls, sprinkle with chopped red pepper, and serve.

Tips

Substitutions/Additions:
Substitute Japanese eggplant or fresh zucchini for the cucumber.
Add Kombu to cucumber.