Scallions thinly sliced on a diagonal, toasted sesame seeds (optional garnish)
1. Finely chop 10 garlic cloves (about 1/2 cup). Place the garlic and 1 tablespoon canola oil in a small saucepan over medium-low heat (this allows the garlic to infuse to the oil as it heats up). Cook, stirring frequently, until the garlic is fragrant and lightly golden-brown, 3 to 6 minutes.
2. Add 1/2 cup soy sauce, 1/2 cup packed light brown sugar, and 1/4 cup rice vinegar. Increase the heat to medium high and bring to a simmer. Meanwhile, place 1 tablespoon cornstarch and 1 tablespoon water in a small bowl and whisk until the cornstarch is suspended.
3. Add the cornstarch slurry to the simmering sauce and cook, whisking often, until bubbling and thickened. Turn off the heat. Add 2 tablespoons gochujang and 2 teaspoons toasted sesame oil, and whisk to combine. Transfer to a large bowl.
Make the fried chicken:
1. Pat 2 to 2 1/4 pounds boneless, skinless chicken thighs dry with paper towels. Cut into rough 2-inch pieces (about 5 per thigh).
2. Make the dredge: Place 1 cup of the cornstarch, 2 teaspoons garlic powder, 1 teaspoon ground ginger, 1/2 teaspoon of the baking powder, 3/4 teaspoon of the kosher salt, and 1/2 teaspoon of the ground white pepper in a medium bowl and whisk to combine.
3. Make the batter: Place the remaining 1 cup cornstarch, 1 teaspoon baking powder, 1 1/2 teaspoons kosher salt, and 1 teaspoon ground white pepper in a second medium bowl. Finely grate 3 garlic cloves and 1/2-inch piece peeled ginger into the bowl. Add 3/4 cup cold water, 1 tablespoon soy sauce, and 1 tablespoon rice vinegar. Whisk until combined.
4. Heat 5 cups canola oil in a heavy-bottomed pot or deep skillet over medium heat until 350 F. (Test if it's hot enough by dropping a bit of the batter into the oil and see if it bubbles immediately, or insert a wooden chopstick and see if bubbles appear.) Meanwhile, line a baking sheet with paper towels or fit with a wire rack. Coat as much of the chicken as you can while the oil heats.
5. Coat the chicken in batches of 8 to 10 pieces: Add to the dredge and toss until evenly coated. Shake off the excess, then add to the batter and toss. Let the excess batter drip off, then return back to the dredge bowl, pressing the cornstarch mixture into the chicken to help create more craggly, crunchy bits. Transfer to a second baking sheet. Rewhisk the batter occasionally as you're coating the chicken, and add a little water as needed if it starts to get too thick.
6. Fry the chicken in batches of 8 to 10 pieces: Add one at a time into the hot oil and fry, stirring occasionally, until cooked through and golden-brown, 6 to 8 minutes. Transfer with a slotted spoon or spider to the wire rack or paper towels. Sprinkle with kosher salt.
7. Toss the chicken in the glaze in batches until evenly coated. Garnish with toasted sesame seeds and sliced scallions, and serve with kimchi ranch and pickled radishes if desired.
Recipe note: The glaze can be made up to one day ahead and refrigerated in an airtight container. Rewarm before using.