Start by making the bao buns.
Place the flour, sugar, salt and yeast in a bowl and mix.
Add the milk, warm water and butter to a jug and stir together until the butter melts. Stir the liquid mixture into the flour mixture at first with a spoon, and then with your hands. Turn out onto a floured surface and knead for 10 minutes. Alternatively, you can do this in a mixer fitted with a dough hook.
Place the dough in an oiled bowl. Cover (with clingfilm or a damp tea towel and leave to prove until doubled in size - about 90 minutes - 2 hours).
Meanwhile, start on the Korean Chicken. Place the chicken in a bowl. Add the buttermilk, salt, pepper and garlic salt—Mix, cover and place in the fridge to marinate for at least 1 hour.
After the dough has proved, tip it out of the bowl onto a floured surface. Knead the dough again and split into 20 balls. Place a piece of baking parchment on your work surface and roll each ball into an oval on top of the parchment, using a rolling pin – approx. 6cm x 9cm.
Brush the ovals with the olive oil and fold each oval over, using a chopstick in the middle to fold over to leave a little space in the fold (so the oil is on the inside of the fold). Remove the chopstick and place each bun onto a small piece of baking parchment.
Place the buns on the trays - still on the baking parchment - as this will help you to move them later. Cover each dish with clingfilm or a carrier bag (ensuring the clingfilm doesn't touch the dough - or it will stick) and leave to prove for a further hour, until puffed up.
Preheat the oven to a low heat (to keep cooked chicken warm). Heat a large pan of vegetable oil (or preheat your deep fat fryer) until hot (you can test by dropping a small cube of bread in there, if it rises immediately to the top and starts to bubble rapidly, it's hot enough). You'll need at least 1 litre (4 cups) of oil.
Mix the crispy coating ingredients in a small bowl. Take the chicken out of the fridge. Lift a piece from the buttermilk and allow the excess to drip off. Dredge the chicken in the crispy coating mixture – ensuring it's fully covered. Place on a tray and repeat until all of the chicken is coated.
Once the oil is hot enough, add in 10-12 of the chicken pieces. You can add more or less depending on the size of your pan, be sure not to overcrowd the chicken. Cook for 3-5 minutes until golden brown and cooked in the middle. You can check this by cutting open a piece of chicken, if it's no longer pink in the centre, it's cooked.
Place on a tray in the oven to keep warm while you cook the rest of the chicken.
Meanwhile, put a large steamer pan on to boil. Working in batches, place the buns in the steamer (you can keep them on the baking parchment and steam for 10 minutes. I use a double layer steam pan - placing four buns in each layer. I once steamed, place on a warm plate.
While the chicken and bao buns are cooking, make the sauce. Place the gochujang, honey, sugar, soy sauce, garlic, ginger, vegetable oil and sesame oil in a saucepan and stir together.
Bring to the boil, then simmer for 5 minutes until thickened.
Place all of the cooked chicken in a bowl and pour the sauce over the chicken. Toss together to coat. You can leave the chicken chunks whole, or slice up if you prefer.
Carefully open the steamed bao buns and stuff with the Korean chicken. Top with slices of red onion, cucumber, fresh coriander (cilantro) and sesame seeds before serving.