Debone the chicken pieces and chop them into bite-sized pieces. Place in a mixing bowl. Then season with mirin, salt and black pepper. Give a mix with your hands. Then set the chicken aside for 20 minutes. Also soak your skewers in another bowl.
Take out a mixing bowl and place all ingredients listed under "Teriyaki Sauce". Give it a nice mix. If you want to make the spicy Gochujang sauce, use the same recipe as the Teriyaki Sauce, but add-in gochujang as well.
Grill chicken and Make Skewers
Measure to the second crease in your pointer finger. Chop spring onion pieces to that length. Make sure to chop-up both the green and white parts of the spring onion. Then put a frying pan on a medium-heat. Put some oil in the pan. Once it is hot, place the chicken pieces in and cook them until they are 80-90% done (when you barely see any pink left). Then set the chicken aside.
Take out the skewers from the water. Add the grilled chicken first onto the skewers. Then add spring onion pieces and alternate. I like to add 4 pieces of chicken to 3 pieces of spring onion. Finally, wrap the end pieces of the skewer with a piece of aluminum foil.
Put frying pan on medium heat. Add oil. Once the pant is hot, place the skewers in. Let it sit there for a minute or two until it develops a nice char and the chicken is fully cooked through. Then flip them over and baste the chicken skewers with the sauce of your choice. Flip around and baste the other side. Turn off heat. Garnish with sesame seeds. Take off the aluminum foil and enjoy.
Place some baby greens in a mixing bowl. Take out another bowl and mix all of the listed ingredients under "Yuja salad dressing". Top the salad with a few spoonfuls of the Yuja dressing. Enjoy and feel elegant!