Prepare the chicken thighs by cutting them into 2 to 3 pieces. They should be about the same size as the bao buns.

For the brine, combine the chicken, milk, garlic, ginger, salt, and black pepper. Set aside for at least 4 hours or overnight.

For the pickled radish, peel the radish and slice it into thin ribbons. Then stack the ribbons and slice them into thin strips. Combine water, sugar, white vinegar, and salt, mixing until dissolved. Transfer the radish into a jar and pour the brine over it until fully submerged. Refrigerate for at least 2 hours.

For the sauce, mix together gochujang, soy sauce, ketchup, rice vinegar, honey, sugar, sesame oil, and grated garlic. Set aside.

Pat dry the chicken pieces with a paper towel and let them air dry at room temperature for 30 minutes.

For the dredge, mix cornstarch, flour, rice flour, baking powder, salt, garlic powder, onion powder, and cayenne pepper together.

For the wet batter, combine 1 cup of the dredge with 2/3 cup cold water. Mix until just combined; the consistency should be like pancake batter.

In a deep pan, heat oil over medium heat to 350°F (175°C).

Dip each chicken piece in the dredge, then into the wet batter, allowing excess to drain. Carefully place in the hot oil and fry for 3 minutes, without overcrowding the pan.

Remove the chicken and place it on a wire rack or a plate lined with paper towels. Repeat with the remaining chicken.

For double frying, increase the oil temperature to 400°F (205°C) and fry for 1 to 2 minutes more until golden brown and crispy.

Brush the sauce onto each chicken piece until fully coated.

To assemble the baos, layer the chicken, pickled radish, scallions, and sesame seeds.