For the marinated ribs:
1) Whisk together soy, groundnut oil, garlic and 2 tbsps of the ginger in a baking dish. Add the ribs and turn to coat. Cover and let marinate in the refrigerator for at least 30 minutes and up to 4 hours.
2) Preheat the barbecue or griddle to high.
3) Season ribs with salt and pepper and barbecue about 3 to 4 minutes per side, until tender.
For the salad:
1) Brush the onions with oil, season with salt and pepper and barbecue for 2 to 3 minutes on each side, until tender.
2) Whisk together the vinegar, remaining tbsp of ginger, honey, sesame oil and olive oil in a large bowl and season with salt and pepper.
3) Coarsely chop the spring onions and add to the bowl. Add mint leaves, mizuna and/or watercress and toss to coat.
4) Serve the salad alongside the barbecued ribs.