These spicy, refreshing cucumbers are a traditional Korean "banchan," or side dish. Danji chef Hooni Kim brines cucumbers in salt before marinating them in Korean red pepper flakes, sugar, and rice vinegar. (Note: Plan ahead for a day of marination.)
Brine cucumbers: Use a mandoline or a sharp knife to cut the cucumbers into ⅓-inch rounds. Place in a colander fitted over a bowl and add salt; mix well to ensure the cucumbers are evenly salted. Let rest at room temperature to drain, 20 minutes. While they drain, prepare the marinade (Step 2).
Marinade: In a large bowl, combine the gochugaru, mirin, rice vinegar, sugar, and fish sauce. Smash and peel the garlic, then finely chop. Use the flat part of your knife to press down on the garlic to further break it down, then continue to mince. Add the garlic to the marinade.
Marinate cucumbers: Rinse all the salt off the cucumbers with cold water. Whisk the marinade, then add the cucumbers; use a large spoon to toss, making sure the cucumbers are evenly coated with marinade. Cover and refrigerate for 1 hour.
Cucumbers will have released more liquid, which helps the marinating process. At this point, they’re ready to eat; however, refrigerating overnight will round out the flavors. Place the cucumbers, along with some marinade, in a lidded container and store in the fridge overnight; serve cold. (The cucumbers can be stored in the refrigerator for 2-3 days, or for as long as the cucumbers remain firm and crunchy.)