Cut the chicken into 1"x1" pieces and place in a large ziplock bag
add the rest of the ingredients, close the bag and massage til fully mixed. Refrigerate at least 2 hours.
In a medium mixing bow whisk together the batter ingredients. Add in the chicken and make sure all pieces are fully covered.
Heat oil in a small pot on high until smoking.
Fry the chicken in batches, 5 minutes per batch til the batter is a dark brown.
While the chicken fries, mix together the sauce ingredients, then add to a small pot and bring to a simmer for 5 minutes. If the sauce thickens too much whisk in a little bit of water.
Slice all the bread in half and butter the insides, place the pieces buttered side up on a baking tray then broil for 1-2 minutes until the edges brown.
Build the sandwiches- bottom to top cucumber, kimchi, chicken, green onion, sauce