Step 1

In a medium bowl, toss cucumbers with salt and, using clean hands, massage cucumbers until they are well coated and just begin to release liquid, about 30 seconds. Transfer cucumbers to a colander; wipe out bowl. Cut a round of parchment paper large enough to cover surface of cucumbers and place over cucumbers. Place a weight on top of parchment to press down on cucumbers (canned goods, a cast iron skillet, a mixing bowl filled with water, or a Chef's Press all make good weights). Set aside to drain for 30 minutes. After 30 minutes, transfer cucumbers to a paper towel-lined plate and blot dry. Set aside.

Step 2

Meanwhile, combine dried radish and 2 cups (475ml) cold water in now-empty bowl. In a separate small bowl, combine sliced onion and 1 cup (240ml) cold water. Soak radish and onion for 20 minutes. After 20 minutes, drain radish and onion, and squeeze out as much water from the radish as possible; discard soaking water. Wipe out both bowls and combine cucumbers, radish, and onion in medium bowl. Add gochugaru and gently massage chile flakes into the vegetables, until they are well-coated and stained bright red, about 30 seconds. Set aside.

Step 3

In now-empty small bowl, whisk together sesame oil, gochujang, vinegar, honey, fish sauce, garlic, and black pepper until well-combined but not fully emulsified. Stir in sesame seeds.

Step 4

Add dressing to vegetables and, using clean hands, toss to combine, massaging dressing into vegetables until they are well coated all over, about 30 seconds. If serving right away, divide between small individual serving bowls, sprinkle with additional sesame seeds, and serve. If making in advance, this banchan can be refrigerated in an airtight container for up to 3 days; bring to cool room temperature before serving. The dressing can also be made in advance and refrigerated in an airtight container for up to 5 days.