Choose meat or chicken. (For easier slicing, chill meat or poultry in freezer until hard but not frozen.) Slice meat or chicken in thin strips. In a bowl, combine soy sauce, Mirin or rice wine vinegar, sesame oil, brown sugar, sweet yellow onion, garlic, 1 tablespoon green onions, ginger, sesame seeds, black pepper and red pepper flakes. Stir well to combine. Place meat or chicken in a glass casserole dish, bowl or pie pan. Pour marinade over meat or chicken and stir well to fully incorporate all of the marinade. Cover and refrigerate for several hours or overnight. When ready to cook, slice slivered onions. Heat oil in cast iron or heavy skillet. Add slivered onions, cooking until soft. With tongs, remove meat or chicken from marinade and add to skillet (don’t overlap the pieces so they can sear on all sides). Cook on medium high for about 5 minutes or until done. Cook until liquid has evaporated and meat or chicken has a rich brown color. Serve immediately with flour tortillas. Sprinkle with remaining tablespoon of green onion.
Note: Korean BBQ Tacos go well with coleslaw. Using store bought packaged cabbage for coleslaw, add a splash of mirin or rice wine vinegar, sesame seed oil, some sesame seeds, salt and pepper to slaw and stir to combine. Serve inside the tacos. This Korean BBQ recipe can also be served with rice.