Spread the pork slices in a shallow bowl. Add the spice mix and work into the meat. Cover and allow to marinate while you prepare the caramelized onion.
Heat the olive oil in a frying pan. Add the onion slices and cook over medium heat, stirring occasionally, until softened and lightly browned. Sprinkle with salt and pepper. Stir to blend. Set aside.
On the stove top grill or in a cast iron pan, spread the pork and cook over high heat until done. Sukiyaki-cut pork is so thin that it's done in just a few minutes.
Assemble the sandwiches. Place one to two slices of pork on a slice of bread, top with caramelized onion, sprinkle with snipped greens, cover with another slice of bread. Serve the pork BBQ mini sandwiches.