For the pulled pork: Rub the pork butt with the salt and brown sugar in a shallow pan. Cover and refrigerate for at least 24 hours.
Preheat the oven to 225 degrees F. Pour out and discard the excess liquid from the pan. Roast the pork, uncovered, until the internal temperature reaches 180 degree F, about 6 hours.
While the pork is roasting, make the quick pickles, kimchi slaw and Korean BBQ sauce.
For the quick pickles: Cut the cucumber into 1/8-inch-thick slices and mix with the salt, sugar and chile flakes in a bowl. Refrigerate until ready to use
For the kimchi slaw: Roughly chop the kimchi and mix with the mayonnaise in a bowl. Refrigerate until ready to use.
For the Korean BBQ sauce: Blend the garlic, ginger, soy sauce, gochujang, brown sugar, vinegar, sesame oil, black pepper, red pepper flakes and onions together in a food processor until well combined.
Remove the pork from the oven and pull into shreds with a fork while still hot. Put the pork in a large bowl, pour over the Korean BBQ sauce and mix well.
To prepare the sandwiches: Put some shredded pork on a roll, top with some kimchi slaw and finish with some quick pickles. Repeat with the remaining rolls and serve.
Cut the cabbage into 1-inch slices, put in a large container, sprinkle with the salt and add about 12 cups (3 quarts) of cold water so the cabbage is just covered. Cover with plastic wrap and refrigerate for 24 hours.
Drain the cabbage and mix with the red pepper powder, fish sauce, ginger, garlic and sugar. Store in an airtight mason jar.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.