Put the sliced onion in a small bowl and mix with the sugar and vinegar. Set aside and allow to marinate.
Broth
Heat some oil in a frying pan. then add the shallot and garlic for 3–4 minutes, or until softened. Add the ginger and Jerk seasoning and cook for a few seconds more, stirring constantly. Pour in the beef broth and add the soy sauce. Bring the liquid to a gentle simmer and cook for 3–4 minutes. Adjust the seasoning to taste, adding a little extra soy sauce if needed.
Steak
Season the steaks with a little salt and pepper then rub the Jerk seasoning over both sides. In a frying pan over high heat, cook the steak for approx. 2 mins on each side. Transfer to a plate and leave to rest.
Noodles and assemble
Cook the noodles according to the packet instructions.(Optional: you can steam some extra vegetables like cabbage, over the noodles)Drain, place into bowls and ladle the broth on top of the noodles. Slice the steak on top. Drain the pickled onions and scatter on top with fresh coriander and chilli flakes.