Score the skin of the duck breast at 2cm intervals, then season with sea salt and black pepper. Place the duck skin-side down in a cold non-stick frying pan, then turn the heat on to medium-high. Cook for 8 minutes without moving it, or until the fat is well rendered and the skin is golden and crispy. Meanwhile, peel and finely slice the ginger and garlic, finely slice the chilli. Snap the woody ends off the asparagus. Turn the duck over and cook for 4 minutes on the other side, then remove to a plate to rest, leaving the pan of duck fat on the heat. Sprinkle the ginger, garlic and chilli into the hot pan and cook for 3 to 5 minutes, or until crisp, stirring regularly. Alongside, blanch or steam the pak choi and asparagus for 2 minutes. Mix the soy sauce and rice vinegar together in a small bowl to make a dressing, adding any resting juices from the duck. Slice the cooked vegetables in half lengthways and arrange on a serving platter. Slice the duck into thin pieces at an angle and arrange over the top. Spoon over the dressing and sprinkle over the crispy ginger, garlic and chilli, to finish.