Separate the tentacles from the tube (reference video below). Then make a cut and throw away the guts that are attached to the tentacles. Put your fingers into the tube and find the 'plastic spine' - pull it out and throw it away. Make a cut just below the eyes of the squid. Throw out that section. Then flip the tentacles up-side down and pop-out the squid beak. Trim the ends off of each tentacle. Then use your fingers and slide it across each tentacles - remove the suction covers. Thoroughly wash both the tentacles and tube. Then place the squid right-side up (fins on top) and turn it ~90 degrees down (reference video). Make cuts along the squid. Set aside.

Mix all of the listed ingredients under 'Gochujang Sauce'. (Note: this will be enough sauce to cover 2 whole squid)

Put a large frying pan on medium-high heat. Pour in some oil. Once the pan is hot, place the squid in (cut-side facing up). Let it cook a few minutes until it starts to turn a red/purple color. Then flip it over. The squid will immediately curl. No worries. Just take two utensils and hold it down flat for ~30 seconds. It should straighten out. Cook until the side is fully cooked thru - with a nice red/purple color. Then turn the heat down to a low. Baste one side with the gochujang sauce. Then flip-it over and baste the other side. Turn off the heat. Plate and garnish it with chives and sesame seeds.